Pat says: If you are already quite familiar with Java, and especially if you are interested in Java as a phenomenon and a platform and not just as a programming language, this is a superb book for learning C#.  It is a scholarly and thorough comparison of the two platforms, as well as a decent reference book for C# programming.  It's full of interesting tidbits about the implementation of the .NET common language runtime (CLR).  It tackles all the hard topics; it is not, however, a book for beginning programmers or non-computer-scientists.