Norman is an excellent writer, and it’s good fun reading his books. If you are interested in DocBook, then get this book:
http://oreilly.com/catalog/9781449389604 = DocBook 5: The Definitive Guide – O’Reilly Media
I purchased the PDF recently from O’Reilly, and I just printed a single page for a friend, who looks like being my newest DocBook proselyte.