In all honesty, this book borders on useless from the perspective of a traveller. It is full of places popular with local expats looking for a bit of home and minimal information about anything actually Chinese. Even the pictures were full of expats! If you rely solely on this book, you will spend most of your time in an expat bubble and see very little of the real Beijing. Lonely planet isn't brilliant on Beijing either, but it's miles ahead of Frommer's.
This book will get you to most of the major tourist spots, but only just barely. As others have said, the accompanying maps are not very detailed and are of little help. At best, they will lead you to the general area you are aiming for, but not much more. Directions and maps for stores and restaurants are absolutely horrible. I ended up mainly using the map that came with the Eyewitness book (the book itself was not any better, but the map was great).
The one thing I will say in the author's defense is that China is growing so quickly that you can't reasonably expect any guide book to be perfectly up to date. There is no way to keep up, so you can't hold that against the author here.
Bottom line: this book is absolutely not worth your money. I do not write a lot of reviews on Amazon, but felt compelled for this one given how poor it was. A huge disappointment, to say the least.