I'm really impressed with this book. It doesn't go through a long overview of the desktop, the apps, the history of Ubuntu, or how to install Ubuntu. Sure, it does go into those subjects a little bit but it manly is a book full of tips and hacks. It is organized in a way that you can just look at the index find a tip that interests you then just read that tip, you don't have to read cover to cover if you don't want to.
Bottom line: If you use Ubuntu you should consider buying this book. Whether you are a beginner or advance user, with 315 tips I'm sure you will find some helpful tips! I personally found this book made Ubuntu more fun! besides there is a cute kitten on the cover, that should be a good reason to buy this book :)