For C#, the book I always find myself going back to is C# In Depth by Jon Skeet. It's one of the most accessible books I've read, and it's one I always recommend to other devs that are interested in the language.
http://meta.stackexchange.com/questions/9134/jon-skeet-facts
My favourite:
Jon Skeet is immutable. If something's going to change, it's going to have to be the rest of the universe.