diff --git a/.gitignore b/.gitignore
index fd3b3b874e30a8e9e615b62f852a485cbf273049..dd4464b64c7f1192bffd6cde2c7ad6226f1ea027 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,6 @@
-.gradle
+.bundle
 /build/
+/Gemfile.lock
+/vendor/bundle
 
 combined.bib
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 3b343d1d19e1e3527e0c0b13308468e5bc7625dc..a534c40e1cf70f98565f550e7dfb78ffaf1e9b6b 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -1,26 +1,14 @@
-variables:
-  DEBIAN_FRONTEND: noninteractive
-  GRADLE_OPTIONS: --info --stacktrace --warning-mode=all
-
-default:
-  image: openjdk:8-jdk-slim
-  cache:
-    paths:
-      - .gradle/caches
-      - .gradle/native
-      - .gradle/wrapper
-  before_script:
-    - apt-get update
-    - apt-get install --assume-yes graphviz
-    - export GRADLE_USER_HOME="${PWD}/.gradle"
-
 asciidoctor:
   stage: build
+  image: asciidoctor/docker-asciidoctor:1.34
+  before_script:
+    - apk update
+    - apk add graphviz
   script:
-    - ./gradlew ${GRADLE_OPTIONS} asciidoctor
+    - make -j2
   artifacts:
     paths:
-      - build/docs/asciidoc
+      - build
 
 upload:
   stage: deploy
@@ -32,4 +20,4 @@ upload:
     - apk add lftp openssh-client
   variables:
     DEPLOY_REMOTE_BASEDIR: stupshome/stups
-  script: LFTP_PASSWORD="${DEPLOY_PASSWORD}" lftp -c "set sftp:auto-confirm yes; open --user ${DEPLOY_USERNAME} --env-password sftp://${DEPLOY_HOST}/${DEPLOY_REMOTE_BASEDIR}/handbook/prob2/; mput -e build/docs/asciidoc/pdf/*.pdf build/docs/asciidoc/html5/*.html; mput -e -O images/ build/docs/asciidoc/html5/images/*; exit"
+  script: LFTP_PASSWORD="${DEPLOY_PASSWORD}" lftp -c "set sftp:auto-confirm yes; open --user ${DEPLOY_USERNAME} --env-password sftp://${DEPLOY_HOST}/${DEPLOY_REMOTE_BASEDIR}/handbook/prob2/; mput -e build/*.html build/*.pdf; mput -e -O images/ build/images/*; exit"
diff --git a/Gemfile b/Gemfile
new file mode 100644
index 0000000000000000000000000000000000000000..c03e993c87305b4a07d18f2547d52ad9ec6d6cc5
--- /dev/null
+++ b/Gemfile
@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+source "https://rubygems.org"
+
+gem "asciidoctor", "~> 2.0"
+gem "asciidoctor-bibtex", "~> 0.8"
+gem "asciidoctor-diagram", "~> 2.0"
+gem "asciidoctor-pdf", "~> 2.0"
+gem "coderay", "~> 1.0"
diff --git a/Makefile b/Makefile
index ed281a1660e23ed3eb88253236ccad4b7fdc893a..08d416c212679ebe0de793305fe4fd8a7f0ba690 100644
--- a/Makefile
+++ b/Makefile
@@ -1,11 +1,35 @@
-run:
-	rm -f build/asciidoc/pdf/*.pdf
-	JAVA_OPTS="-Xmx2G" ./gradlew --no-daemon asciidoctor
-view:
-	open build/asciidoc/pdf/prob_user_manual.pdf
-viewd:
-	open build/asciidoc/pdf/prob_developer.pdf
-fullclean:
-	gradle clean
+ASCIIDOCTOR := asciidoctor
+ASCIIDOCTOR_PDF := asciidoctor-pdf
+ASCIIDOCTOR_OPTIONS := \
+	--attribute imagesoutdir=build/images \
+	--require asciidoctor-bibtex \
+	--require asciidoctor-diagram \
+
+BIBTEX_FILES := $(wildcard src/docs/bibtex/*.bib)
+COMBINED_BIBTEX_FILE := src/docs/asciidoc/combined.bib
+
+MAIN_FILE := src/docs/asciidoc/prob_handbook.adoc
+CHAPTER_FILES := $(wildcard src/docs/asciidoc/chapter/Java_API/*.adoc)
+
+.PHONY: all
+all: build/prob_handbook.html build/prob_handbook.pdf
+
+$(COMBINED_BIBTEX_FILE): $(BIBTEX_FILES)
+	cat $^ > $@
+
+build/prob_handbook.html: $(MAIN_FILE) $(CHAPTER_FILES) $(COMBINED_BIBTEX_FILE)
+	$(ASCIIDOCTOR) $(ASCIIDOCTOR_OPTIONS) --destination-dir $(@D) --source-dir $(<D) $<
+	cp src/docs/asciidoc/images/*.png build/images
+
+build/prob_handbook.pdf: $(MAIN_FILE) $(CHAPTER_FILES) $(COMBINED_BIBTEX_FILE)
+	$(ASCIIDOCTOR_PDF) $(ASCIIDOCTOR_OPTIONS) --destination-dir $(@D) --source-dir $(<D) $<
+
+.PHONY: html
+html: build/prob_handbook.html
+
+.PHONY: pdf
+pdf: build/prob_handbook.pdf
+
+.PHONY: clean
 clean:
-	rm build/asciidoc/pdf/*.pdf
\ No newline at end of file
+	$(RM) -r build $(COMBINED_BIBTEX_FILE)
\ No newline at end of file
diff --git a/README.adoc b/README.adoc
index 17b484214f3b3f41e078ab5ffe5601b97e3430f2..4d662d1391de7ddd56a0a9493aab58039df1ee39 100644
--- a/README.adoc
+++ b/README.adoc
@@ -6,3 +6,30 @@ Repository for the ProB 2.0 Developer and User Handbook.
 
 * The handbook is located at https://www3.hhu.de/stups/handbook/prob2/prob_handbook.html
 * A PDF is available from https://www3.hhu.de/stups/handbook/prob2/prob_handbook.pdf
+
+== Building
+
+Assuming you have all necessary dependencies installed (see below), run:
+
+[source,sh]
+----
+$ make
+----
+
+The documentation will be built in HTML and PDF format and output into the build directory.
+
+== Dependencies
+
+The build requires https://asciidoctor.org/[Asciidoctor] with the https://github.com/asciidoctor/asciidoctor-bibtex[BibTeX], https://docs.asciidoctor.org/diagram-extension/latest/[diagram], and https://docs.asciidoctor.org/pdf-converter/latest/[PDF] extensions.
+These dependencies are available in most package managers
+and as a Docker image https://github.com/asciidoctor/docker-asciidoctor[asciidoctor/docker-asciidoctor].
+
+You can also use an existing https://www.ruby-lang.org/[Ruby] installation and https://bundler.io/[Bundler] to install the dependencies:
+
+[source,sh]
+----
+$ bundle config set --local path vendor/bundle
+$ bundle install
+----
+
+Then use `bundle exec make` to run the build.
diff --git a/build.gradle b/build.gradle
deleted file mode 100644
index cc56ee1f56bba88a4ee59b3f88552cd195196c6f..0000000000000000000000000000000000000000
--- a/build.gradle
+++ /dev/null
@@ -1,69 +0,0 @@
-plugins {
-    id "org.asciidoctor.jvm.convert" version "3.3.2"
-    id "org.asciidoctor.jvm.gems" version "3.3.2"
-    id "org.asciidoctor.jvm.pdf" version "3.3.2"
-}
-
-wrapper {
-    gradleVersion = "7.4.2"
-}
-
-repositories {
-    mavenCentral()
-    ruby.gems()
-}
-
-dependencies {
-    asciidoctorGems 'rubygems:asciidoctor-bibtex:0.8.0'
-    // asciidoctor-bibtex depends on version 1.x of citeproc-ruby and csl-styles,
-    // but for some reason the build installs version 2.x by default.
-    // To fix this we need these manual dependencies on the 1.x versions.
-    asciidoctorGems 'rubygems:citeproc-ruby:1.1.14'
-    asciidoctorGems 'rubygems:csl-styles:1.0.1.11'
-}
-
-task bibtex() {
-    def inputDir = file("src/docs/bibtex")
-    def combinedFile = file("src/docs/asciidoc/combined.bib")
-    inputs.dir(inputDir)
-    outputs.file(combinedFile)
-
-    doFirst {
-        combinedFile.text = fileTree(inputDir) {
-            include "**/*.bib"
-        }.collect {it.text}.join("\n")
-    }
-}
-
-asciidoctor {
-    dependsOn = [bibtex, asciidoctorGemsPrepare]
-
-    outputOptions {
-        backends = ['html5', 'pdf']
-    }
-
-    asciidoctorj {
-        modules {
-            diagram.use()
-        }
-        requires = ['asciidoctor-bibtex']
-    }
-
-    baseDirFollowsSourceDir()
-
-    sources {
-        include '*.adoc'
-    }
-
-    resources {
-        from('src/docs/asciidoc') {
-            include '**/*.png'
-        }
-    }
-}
-
-clean {
-    delete('src/docs/asciidoc/combined.bib')
-}
-
-defaultTasks 'asciidoctor'
diff --git a/gradle/wrapper/gradle-wrapper.jar b/gradle/wrapper/gradle-wrapper.jar
deleted file mode 100644
index 41d9927a4d4fb3f96a785543079b8df6723c946b..0000000000000000000000000000000000000000
Binary files a/gradle/wrapper/gradle-wrapper.jar and /dev/null differ
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
deleted file mode 100644
index aa991fceae6e464c320a107e4b337daf48c0d7ab..0000000000000000000000000000000000000000
--- a/gradle/wrapper/gradle-wrapper.properties
+++ /dev/null
@@ -1,5 +0,0 @@
-distributionBase=GRADLE_USER_HOME
-distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-7.4.2-bin.zip
-zipStoreBase=GRADLE_USER_HOME
-zipStorePath=wrapper/dists
diff --git a/gradlew b/gradlew
deleted file mode 100755
index 1b6c787337ffb79f0e3cf8b1e9f00f680a959de1..0000000000000000000000000000000000000000
--- a/gradlew
+++ /dev/null
@@ -1,234 +0,0 @@
-#!/bin/sh
-
-#
-# Copyright © 2015-2021 the original authors.
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#      https://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-#
-
-##############################################################################
-#
-#   Gradle start up script for POSIX generated by Gradle.
-#
-#   Important for running:
-#
-#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
-#       noncompliant, but you have some other compliant shell such as ksh or
-#       bash, then to run this script, type that shell name before the whole
-#       command line, like:
-#
-#           ksh Gradle
-#
-#       Busybox and similar reduced shells will NOT work, because this script
-#       requires all of these POSIX shell features:
-#         * functions;
-#         * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
-#           «${var#prefix}», «${var%suffix}», and «$( cmd )»;
-#         * compound commands having a testable exit status, especially «case»;
-#         * various built-in commands including «command», «set», and «ulimit».
-#
-#   Important for patching:
-#
-#   (2) This script targets any POSIX shell, so it avoids extensions provided
-#       by Bash, Ksh, etc; in particular arrays are avoided.
-#
-#       The "traditional" practice of packing multiple parameters into a
-#       space-separated string is a well documented source of bugs and security
-#       problems, so this is (mostly) avoided, by progressively accumulating
-#       options in "$@", and eventually passing that to Java.
-#
-#       Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
-#       and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
-#       see the in-line comments for details.
-#
-#       There are tweaks for specific operating systems such as AIX, CygWin,
-#       Darwin, MinGW, and NonStop.
-#
-#   (3) This script is generated from the Groovy template
-#       https://github.com/gradle/gradle/blob/master/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
-#       within the Gradle project.
-#
-#       You can find Gradle at https://github.com/gradle/gradle/.
-#
-##############################################################################
-
-# Attempt to set APP_HOME
-
-# Resolve links: $0 may be a link
-app_path=$0
-
-# Need this for daisy-chained symlinks.
-while
-    APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
-    [ -h "$app_path" ]
-do
-    ls=$( ls -ld "$app_path" )
-    link=${ls#*' -> '}
-    case $link in             #(
-      /*)   app_path=$link ;; #(
-      *)    app_path=$APP_HOME$link ;;
-    esac
-done
-
-APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
-
-APP_NAME="Gradle"
-APP_BASE_NAME=${0##*/}
-
-# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
-DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
-
-# Use the maximum available, or set MAX_FD != -1 to use that value.
-MAX_FD=maximum
-
-warn () {
-    echo "$*"
-} >&2
-
-die () {
-    echo
-    echo "$*"
-    echo
-    exit 1
-} >&2
-
-# OS specific support (must be 'true' or 'false').
-cygwin=false
-msys=false
-darwin=false
-nonstop=false
-case "$( uname )" in                #(
-  CYGWIN* )         cygwin=true  ;; #(
-  Darwin* )         darwin=true  ;; #(
-  MSYS* | MINGW* )  msys=true    ;; #(
-  NONSTOP* )        nonstop=true ;;
-esac
-
-CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
-
-
-# Determine the Java command to use to start the JVM.
-if [ -n "$JAVA_HOME" ] ; then
-    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
-        # IBM's JDK on AIX uses strange locations for the executables
-        JAVACMD=$JAVA_HOME/jre/sh/java
-    else
-        JAVACMD=$JAVA_HOME/bin/java
-    fi
-    if [ ! -x "$JAVACMD" ] ; then
-        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
-
-Please set the JAVA_HOME variable in your environment to match the
-location of your Java installation."
-    fi
-else
-    JAVACMD=java
-    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
-
-Please set the JAVA_HOME variable in your environment to match the
-location of your Java installation."
-fi
-
-# Increase the maximum file descriptors if we can.
-if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
-    case $MAX_FD in #(
-      max*)
-        MAX_FD=$( ulimit -H -n ) ||
-            warn "Could not query maximum file descriptor limit"
-    esac
-    case $MAX_FD in  #(
-      '' | soft) :;; #(
-      *)
-        ulimit -n "$MAX_FD" ||
-            warn "Could not set maximum file descriptor limit to $MAX_FD"
-    esac
-fi
-
-# Collect all arguments for the java command, stacking in reverse order:
-#   * args from the command line
-#   * the main class name
-#   * -classpath
-#   * -D...appname settings
-#   * --module-path (only if needed)
-#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
-
-# For Cygwin or MSYS, switch paths to Windows format before running java
-if "$cygwin" || "$msys" ; then
-    APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
-    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
-
-    JAVACMD=$( cygpath --unix "$JAVACMD" )
-
-    # Now convert the arguments - kludge to limit ourselves to /bin/sh
-    for arg do
-        if
-            case $arg in                                #(
-              -*)   false ;;                            # don't mess with options #(
-              /?*)  t=${arg#/} t=/${t%%/*}              # looks like a POSIX filepath
-                    [ -e "$t" ] ;;                      #(
-              *)    false ;;
-            esac
-        then
-            arg=$( cygpath --path --ignore --mixed "$arg" )
-        fi
-        # Roll the args list around exactly as many times as the number of
-        # args, so each arg winds up back in the position where it started, but
-        # possibly modified.
-        #
-        # NB: a `for` loop captures its iteration list before it begins, so
-        # changing the positional parameters here affects neither the number of
-        # iterations, nor the values presented in `arg`.
-        shift                   # remove old arg
-        set -- "$@" "$arg"      # push replacement arg
-    done
-fi
-
-# Collect all arguments for the java command;
-#   * $DEFAULT_JVM_OPTS, $JAVA_OPTS, and $GRADLE_OPTS can contain fragments of
-#     shell script including quotes and variable substitutions, so put them in
-#     double quotes to make sure that they get re-expanded; and
-#   * put everything else in single quotes, so that it's not re-expanded.
-
-set -- \
-        "-Dorg.gradle.appname=$APP_BASE_NAME" \
-        -classpath "$CLASSPATH" \
-        org.gradle.wrapper.GradleWrapperMain \
-        "$@"
-
-# Use "xargs" to parse quoted args.
-#
-# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
-#
-# In Bash we could simply go:
-#
-#   readarray ARGS < <( xargs -n1 <<<"$var" ) &&
-#   set -- "${ARGS[@]}" "$@"
-#
-# but POSIX shell has neither arrays nor command substitution, so instead we
-# post-process each arg (as a line of input to sed) to backslash-escape any
-# character that might be a shell metacharacter, then use eval to reverse
-# that process (while maintaining the separation between arguments), and wrap
-# the whole thing up as a single "set" statement.
-#
-# This will of course break if any of these variables contains a newline or
-# an unmatched quote.
-#
-
-eval "set -- $(
-        printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
-        xargs -n1 |
-        sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
-        tr '\n' ' '
-    )" '"$@"'
-
-exec "$JAVACMD" "$@"
diff --git a/gradlew.bat b/gradlew.bat
deleted file mode 100644
index ac1b06f93825db68fb0c0b5150917f340eaa5d02..0000000000000000000000000000000000000000
--- a/gradlew.bat
+++ /dev/null
@@ -1,89 +0,0 @@
-@rem
-@rem Copyright 2015 the original author or authors.
-@rem
-@rem Licensed under the Apache License, Version 2.0 (the "License");
-@rem you may not use this file except in compliance with the License.
-@rem You may obtain a copy of the License at
-@rem
-@rem      https://www.apache.org/licenses/LICENSE-2.0
-@rem
-@rem Unless required by applicable law or agreed to in writing, software
-@rem distributed under the License is distributed on an "AS IS" BASIS,
-@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-@rem See the License for the specific language governing permissions and
-@rem limitations under the License.
-@rem
-
-@if "%DEBUG%" == "" @echo off
-@rem ##########################################################################
-@rem
-@rem  Gradle startup script for Windows
-@rem
-@rem ##########################################################################
-
-@rem Set local scope for the variables with windows NT shell
-if "%OS%"=="Windows_NT" setlocal
-
-set DIRNAME=%~dp0
-if "%DIRNAME%" == "" set DIRNAME=.
-set APP_BASE_NAME=%~n0
-set APP_HOME=%DIRNAME%
-
-@rem Resolve any "." and ".." in APP_HOME to make it shorter.
-for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
-
-@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
-set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
-
-@rem Find java.exe
-if defined JAVA_HOME goto findJavaFromJavaHome
-
-set JAVA_EXE=java.exe
-%JAVA_EXE% -version >NUL 2>&1
-if "%ERRORLEVEL%" == "0" goto execute
-
-echo.
-echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
-echo.
-echo Please set the JAVA_HOME variable in your environment to match the
-echo location of your Java installation.
-
-goto fail
-
-:findJavaFromJavaHome
-set JAVA_HOME=%JAVA_HOME:"=%
-set JAVA_EXE=%JAVA_HOME%/bin/java.exe
-
-if exist "%JAVA_EXE%" goto execute
-
-echo.
-echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
-echo.
-echo Please set the JAVA_HOME variable in your environment to match the
-echo location of your Java installation.
-
-goto fail
-
-:execute
-@rem Setup the command line
-
-set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
-
-
-@rem Execute Gradle
-"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
-
-:end
-@rem End local scope for the variables with windows NT shell
-if "%ERRORLEVEL%"=="0" goto mainEnd
-
-:fail
-rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
-rem the _cmd.exe /c_ return code!
-if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
-exit /b 1
-
-:mainEnd
-if "%OS%"=="Windows_NT" endlocal
-
-:omega
diff --git a/settings.gradle b/settings.gradle
deleted file mode 100644
index a5ea587b066e9f2064432729042ac14a5d05fa4b..0000000000000000000000000000000000000000
--- a/settings.gradle
+++ /dev/null
@@ -1 +0,0 @@
-rootProject.name = "prob2-doc"
diff --git a/src/docs/asciidoc/prob_handbook.adoc b/src/docs/asciidoc/prob_handbook.adoc
index b071a6a9257a8e80947e88471297a3acea8b0c3c..50ee94529f30b46c595343dba0636ee08f5aa8d8 100644
--- a/src/docs/asciidoc/prob_handbook.adoc
+++ b/src/docs/asciidoc/prob_handbook.adoc
@@ -1,6 +1,6 @@
 = ProB Handbook
 Jens Bendisposto;Joy Clark;Michael Leuschel
-:bibtex-file: combined.bib
+:bibtex-file: src/docs/asciidoc/combined.bib
 :coderay-linenums-mode: table
 :doctype: book
 :icons: font