This book is a treasure trove of information; it's well defined and very informative. There is a great bit of information that is not found in the MSDN libraries. You will find throughout the book many notes that give you additional information about the given subject.
After reviewing this book I would recommend it for anyone who likes to have a good reference book at their finger tips. My only regrets are the fact that everything is written in C# and the fact that in the Foreward the author takes the time to vindicate C# as the best language to use in .NET. It's one thing to put all your examples in C# it's another to call it the .NET Framework Standard Library Annotated Reference if it's really a "C# Standard Library Annotated Reference." The .NET framework is designed to bring us together, though books as these tend to split us apart.
What I found to be worth more than the book is the included CD. I go back to my previous statement; I can understand only using C# in writing the book (for fewer pages), but on the CD they have more flexibility to do a lot more and provide some examples in the other popular .NET languages.
Overall, it is a great reference, and I love the poster provided.