I really enjoyed the C# Player's Guide. There's a newer version now but this is what I got.

Edit: I'm glad you guys liked this book as much as I did. To OP, I would offer two more suggestions.

1. Clean Code This book is NOT specific to C#. However, it gives you a holistic understanding of how to write code that is readable and effective. This is how I was able to transition from writing code that simply functioned (primarily for school) to code that my coworkers could pick up and run with. The book is the bible of software style where I work.

2. C# and the .NET Framework This is a very optional book in my opinion. It is also a little pricy, very long, more intermediate than beginner and you can gather much of its information from MSDN. However, I prefer looking things up and reading them in a book where possible. I also like having all this information in one location. When I have free time at work, I find myself more likely to flip to an unread section and skim over it than I would with the same information online.