I like C# 3.0 cookbook very much as reference book. Can anyone suggest any better ?
C# 3.0 in a Nutshell by O'Reily is pretty handy.
The examples are very concise, the content covers a large part of the framework for such a tiny book, and there are helpful "gotcha" tips scattered around.
I can't compare this with other books but its always done the job when google or msdn docs weren't available.
I guess Jon Skeet is too modest to mention it, but his book "C# in Depth" is a great book which concentrates on C#3.
Pro c# with .net 3.0 by Andrew Troelsen is pretty good Also C# 3 in a nutshell
Without a doubt, you must have Juval's book, Programming .NET Components.
The Wrox books are always good. Check out C# 2008 and ASP.Net 3.5 http://www.wrox.com/WileyCDA/
In response to AJ I'd add More Effective C# by Bill Wagner. It covers C# 2 and 3 in depth and, like its predecessor, is very accessible.
Just wanted to say that I'm into the 3.0 chapters in C# in Depth, and I really love the book so far.