Unfolding Java Transactions Open Book
This book is meant to be written in an open-source manner and the reason for writing it may be found here.
This book is written using Asciidoctor for it offers:
a text-based document format, which eases collaboration and change tracking on GitHub
PDF, DocBook, HTML5 support
a rich set of tools like:
You can find an Asciidoctor quick reference here.