If you are looking for a book that nicely summarizes the C# language into a (non-MSDN) text, then this does a good job. It is well organized and keywords, functions, statements, etc are easy to find and cross-reference. The sample code is relatively useful, but sometimes challenging to figure out. I'd therefore recommend this book for intermediate-to-experienced C# developers.

The trend of putting help and documentation online is not a bad idea per se, it's certainly cheaper for development houses than printing expensive paper manuals. But, although the capability for the 'paperless' office is here, the office itself isn't. This is because printed material is still the most versatile way for people to use and handle.
Online helps and references are sometimes like mazes, in that you chase a topic in a big circle until you get back to the beginning. They are great for overview and organization, lousy for hunting specifics. In addition, unless you have a laptop, you can't curl up in bed and read.
While it's true that everything in the printed reference is already in online help I've always found it convenient to also acquire the printed documentation. It's easier to park a specific page open and refer to it than to hop from one screen to another. Snippets of example code serve to illustrate the practical implementations of various C# elements.