Not only does the book give you a good insight on the features of the framework, but it also digs deep into the inner working of the CLR giving the reader a great knowledge on how to write code that runs under the .NET framework.
The book analyses how the CLR handles our code, how and when it gets converted into intermediate language, how it gets executed and -more importantly- how the developer can interfere with this behavior and get the best out of the framework.
Furthermore, the book explores the fundamentals of the framework; including data types, methods, events, interfaces, generics ... etc. These are the basics of the framework that we all know about but the book explains them in detail so you learn what to use when.
The author, who has extensive experience in the framework since its beginnings, puts the picture clear to the reader about what features of the framework are better be avoided and which of them should be used with caution. Not all features are made for all scenarios!
On the other hand, the book introduces some features that we rarely use or might not know about at all. It also illustrates the best way of using some features that we're familiar with in order to shorten our tasks or make our code more efficient and reliable.
In brief, I think this is a must-read book by every .NET developer.