Bob Stayton has released DocBook XSL: The Complete Guide, an online book covering "all aspects of DocBook XML publishing tools, including
installing, using, and customizing the XSL stylesheets and processing
tools."
A PDF version of the guide is available for purchase; an HTML version of the full text is also available online.
It is a massive guide, weighing in at 26 chapters (300+ letter-size pages), with step-by-step instructions on everything from tool setup to customizing output to stylesheet debugging.
Stayton has some first-rate qualifications for
authoring such a guide. He's a member of the DocBook Technical Committee at OASIS, responsible for overseeing changes to the DocBook vocabulary itself, and one of the most active contributors
to discussions on the docbook-apps mailing list, often tackling questions from new users or following up on bug
reports from the field.
Also, along with Jirka Kosek,
he's a major contributor to development of the
DocBook XSL stylesheets (created by Norm Walsh, who also continues to do principal development on them). Among a variety of bug fixes and smaller enhancements, he's responsible for contributing the implementation of XSLT support for the DocBook Olink
element, a sophisticated system that enables relative links to be maintained among rendered DocBook documents -- covered in detail in the book.