I've pretty much read most of the XNA books available. A lot of them will explain how XNA works, but fail to take the reader through the completion of a significant game. I feel that hand holding a person through the creation of complete, sufficient, healthy games is more important in the long run than explaining exactly what each overloaded SpriteBatch.Draw() method does (that's what MSDN is for). Sure, you need to explain to the reader how sprites are drawn to the screen, but you don't need to go crazy with the specifics. This book explains enough to the reader so they have a understanding of what's going on, without bogging them down with too much information.
XNA 4.0 Game Development by Example wastes no time in diving into code, creating what is exceedingly a simple game, but builds a strong foundation for the other games which will be built. The reader will learn by doing, progressively increasing their knowledge of XNA and learning how to develop a game. There are times when the author will gloss over specific details, details that I feel should have been explained a bit more, but any successful programmer will investigate topics of interest on their own anyways.
The book doesn't assume any previous C# knowledge, or programming knowledge if I'm not mistaken. I'm going to raise a huge flag and say you should be a competent programmer before diving into this book. Don't get this book if you've never written any type of program on your own, and I'm not talking about just a "Hello World" program either. I promise that you really won't understand what's going on and once you leave sample land, you'll be completely lost. Understand that game programming is an extremely elitest form of software development, even with XNA. So with that said, this book is aimed at complete beginners to XNA and game programming, but not programming in general. You may do alright if you don't know C# yet, but do know Java (preferably) or even C++.
Also note, this book doesn't explain anything specific to Windows Phone 7 game programming. If Windows Phone 7 game programming is your ultimate goal, you can still use this book to learn XNA, and then move onto the many tutorials and guides available on the new App Hub website.