C# 5.0 in a Nutshell 5e

Gives a good overview of the language, with a nice amount of detail and pretty straightforward to understand. If you need a general book on C# then this will do you just fine. The only complaint I have is that it has a lot of chapters on non-core parts of the language, such as LINQ and XML, which I think would be better suited to a separate book, as I (and most people I imagine) expect 'XXX in a Nutshell' books to be fairly compact and focused on the core subject.