Should this review be just 140 characters? I don't think it would be helpful; or how about: "Great book. Buy it. Great for newbies and sort-of-newbies."
I had been on Twitter for several months, but could never really get a handle on what the benefits were, how to "talk the Twitter language" and how to manage all the tweets I was getting.
Yes, the book starts with the basics of signing on (well, it IS a "Dummies" book), but even some of the basics were things I needed to know. The authors are also very upfront that things are constantly changing; but this being Twitter, they'll also provide updates via @dummies.
The book is well organized and answered all my questions so that I'm not afraid to go online (or on-mobile!) and dive in. In fact, the authors encourage you to jump into conversations and not be shy.
Lots of good tips, lots of things to do on Twitter.
If you've been using Twitter for a while and feel you know you way around, this book isn't for you. It's for the rest of us--those of us who may have put our toes in but needed to be up to submerge ourselves (bad metaphor?), or for those who may have been afraid of this new social medium. Happy tweets!