Let me state publicly for the record: I do not approve of books for learning C#. The only guide you will ever need is the ECMA-334 standard. It's a readable guide to the entire C# language that covers every facet of the language. This document is the definitive guide for C#. In fact, there is no document on MSDN that even comes close to the comprehensive native of C# than does the ECMA-334 standard as the ECMA-334 standard *is* C#.
Why do I mention this at all? Because, from time to time I get people asking me what book he or she should *buy* to learn C# and I always tell them what I've just stated above. Unlike Visual Basic, C# is NOT Microsoft's baby. They may have been the ones who gave birth to C# and continue feed it and nurture it, but it's a standard -- not Microsoft's baby.
Lastly, while you are getting the ECMA-334 standard, check out the ECMA-335 standard. This one is the standard for the CLI (Common Language Infrastructure -- which Microsoft implements as the CLR or Common Language Runtime). It goes into detail about the IL (Intermediate Language), the Common Language Specification (CLS), the Common Type System, and talks in some detail about various .NET concepts. I would consider this standard to be more advanced than what most people need at first, so I don't recommend this for initial learning (for that get Duffy's Professional .NET Framework 2.0 [0764571354] and then Richter's CLR via C# [0735621632]).
As a footnote, you could also check out the ECMA-262 standard (ECMAScript, that is, JavaScript), but it's not nearly as well written as the ECMA-334 and ECMA-335 standards and because of that I've never recommended it's reading to anyone.
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