If you share some of my interests (like writing clean code, or, even better, writing clean code in C#), you'll already know and love Jon Skeet's Coding Blog. If you enjoy Jon's blog as I do, then there's some really good news: Jon has actually written a book about C# called C# in Depth (http://csharpindepth.com). Manning publications was even kind enough to provide me with a free copy of the book, which is greatly appreciated.
Now, this is not a usual C# book that just rewrites the spec in a human-readable form. C# in Depth is far from being a boring description of numeric types and for/while/do/break/continue constructs. It shows the most interesting and shiny aspects of the language and provides interesting background and insight on why the feature was introduced and what's the best way to use it. Moreover, Jon does a great job at comparing how to achieve the same results in C# 1.0, 2.0 and 3.0 - and I have to admit, the 3.0 version always looks aesthetically pleasing and way better than the earlier versions. Mastering lambdas, anonymous types & Co is something very important for developing a good programming style and the book will teach exactly that - how to write clean, elegant, beautiful code given all the power of the C# language.
I really enjoyed the book and I highly recommend it. Thanks Jon!