The content of this book ships with the MSDN library for Visual Studio.Net, at least most of it. The book drops out some of the holes in the MSDN library, which gives it a slight advantage.
As far as technical merit, this book rates above the rest of the C# books, with perhaps the exception of Gunnerson's book, which is sometimes a bit harder to read for understanding. Funny comment actually, since this is a spec doc and his book is supposed to teach.
The best book of the lot, as far as learning goes, is the Wrox book. Unfortunately, it is a bit inconsistent and goes from strong to weak depending on which chapter you read. It also spends a lot of time on the tools, which is not the reason you buy a book on a language.
If you are an experienced or intermediate developer, you can get a lot out of this book. If you are a beginner, I might hold off for something a bit easier to read through. You can get through this book, but I believe Inside C# or Wrox's book might be a better starting point.