If you have been a designer for the past five years and have some experience with touchscreen or interactive surfaces of one kind or another, then Designing Gestural Interfaces is not for you. This book is best for the beginner as its content is very basic and superficial. There is no deep thinking or insights here. Unfortunately, the occassional good topic is glossed over and your left with only the beginning of an idea.
It's true that designing for gestural interfaces is a relatively new area, but the author presents the reader with general and basic design information that has been known and practiced for many years and not nearly enough useful information about gesture design. For example, in the chapter on Prototyping Interactive Gestures, the author talks about the purpose and value of low-fidelity prototyping, but offers nothing related to gestural UI design; no hints, tips, tricks, pitfalls, solutions, etc. In this regard, I found myself getting frustrated many times throughout the whole book.
In general, the book reads like an introductory design book, a primer of sorts, updated to include gestures. I suspect that within the next year or so, updated versions of this book or even other books / articles will come out that offer much deeper insights. If you're a veteran designer, save your money and spend your time wisely reading other more insightful books.