Recommended reading
C# in a Nutshell by Joseph and Ben Albahari
It covers a lot (all?) topics you may need on the day to day basis when you write C# code. Contains info about language and framework basics as well as base class library overview.
C# in Unleashed by Bart De Smet
Although covers similar material as in “C# in a Nutshell”, Bart does it from a different angle with a lot of interesting stories. (Do you know why we have “little-endian” and “big-endian” byte ordering?) I use this book quite often since it has a lot of details (usually not so straightforward as you may think).
Framework Design Guidelines by Krzysztof Cwalina, Brad Abrams
This book contains simple DOs and DO NOTs recommendations. Although simple, the whole framework is built based on these rules. Highly recommended for experienced developers.
C# 4.0 The Complete Reference by Herbert Schildt
This is the book I used when I started learning C# and .NET. I didn’t know much about programming then but this book is not hard in terms of understanding. I didn’t finish it though because when I got main ideas I switched to Troelsen book. Recommended for beginners.