When the subject of the book is clear for you and you understand it is all about the even smallest details of C#, you’ll just love this book! It goes to the most unbelievable details in explaining all the concepts and giving all the definitions. Basically it tells you all what there is to be told.
Another great thing is that the book is very well organized. You don't have to dig through the whole book to search for certain thing, but you can just read the certain chapter or even paragraph. Most of the things are covered in the .NET Framework documentation, but a book like this is very welcome to ease the burden of searching details from documentation, which can sometimes be very annoying, especially if the information is not easily available.
And of course, information about the next version of C# is always interesting
Due to the chosen subject, this isn’t the easiest book to read and especially it isn't such that you'd read every day. The language used is very technical and explanations lean on theory, not necessarily on practical concepts. So this book isn't the best choice for beginners. It takes time to read and even more time to understand what the book tells about.
Another thing is that the book is written with quite flat style meaning that there isn't any personal touch on the writing. It is pretty much like the documentation in .Net Framework SDK. It tells you things and that's it.