Simply put, this is the best book on Motion Graphics for After Effects. Nothing comes close. Buy it -- I guarantee you won't be disappointed.
I first came across this "book" a number of editions ago when it was split across 2 volumes, "the Essentials" and "Advanced Techniques." Thinking back I remember feeling dumbfounded. It's very rare to find a book that's written and illustrated so well. It's even rarer to find an individual that is both a sought after expert in his or her field, who also has an extraordinary talent for teaching. As if that wasn't enough, there was not one but two of these amazingly talented individuals authoring these volumes.
With this 5th edition that has been updated for Adobe CS5 the winning formula is the same. The book is jam packed with clear descriptive text, beautiful full color images, sidebars containing tips and a DVD containing extremely well organized example projects with yet more articles on expression and effects (checkout Chris and Trish Meyer's articles on Artbeats or Provideo Coalition (where you will find their blog).
The book seems expensive at $70, but it's worth every penny and extremely good value considering the content and depth the book covers (I've been using After Effects for ten years, and I'm still finding nuggets in this book). If you plan on using After Effects as part of a post production movie making, then you may find the coverage of rotoscoping, motion tracking and color grading a little light (and for this I'd recommend Mark Christiansen's excellent After Effects CS5, Visual Effects and Compositing, Studio Techniques).
As a study in Motion Graphics, I can't find fault with the book at all. If you are any way involved in After Effects and motion graphics, this books needs to be in you library. Enough said.