I got this one out of the library as I have just bought my first Android Tablet and wanted to make sure I wasn't missing anything obvious. The short answer is, not very much, as most of what this book was saying was stuff I had managed to work out for myself by just playing with it. There were a few tips I picked up though, in the sections I read (I skipped over some of the bits that either were not available on my tablet or were stuff that I wasn't likely to use).
However, like all Dummies books, it is written in an amusing and informal way that makes you feel like you've been entertained as well as educated.