Authors of any coding system know that language specifications are useful for syntax issues, but don't help with how-tos and best practices. Tony Self's wonderful DITA Style Guide bridges that gap with insight and clarity, explaining not just how to use virtually every DITA construct (including 1.2), but why you might use one over another, as well as when (and when not!) to use them.
I don't agree with the author's introductory assertion that it's not a "good read" -- I find it thoroughly engrossing, and tend to read it like a hyperlinked web site, jumping about from subject to subject, learning something new at every stop. In fact, I use this book so much that I soon bought a second copy and had it spiral bound ($5 at Kinko's) so it would lay flat on my desk, further increasing its value and usefulness.
This book is filled with clear, accurate, well-described examples, and is written in Tony's easygoing style, turning otherwise dry reference material into accessible and useful guidelines for writing better DITA code.
If you work in DITA at any level, you can't afford not to have this book!