Listmania!
C# developer's bookshelf
Code Complete: A Practical Handbook of Software ConstructionCode Complete: A Practical Handbook of Software Construction by Steve McConnell
Buy new: £21.80 / Used from: £18.99
OK, not a C# specific book but required reading for developers.
Writing Secure Code 2nd EditionWriting Secure Code 2nd Edition by Michael Howard and David LeBlanc
Buy new: £22.05 / Used from: £8.50
Don't let your code out into the big bad world without reading this first.
Applied Microsoft .NET Framework ProgrammingApplied Microsoft .NET Framework Programming by Jeffrey Richter
Buy new: £28.57 / Used from: £11.95
My guess is that this will become the standard text on the .Net CLR. Detailed and well written.
Windows Forms Programming in C# (Microsoft .Net Development)Windows Forms Programming in C# (Microsoft .Net Development) by Chris Sells
Buy new: £32.29 / Used from: £9.99
I have to admit I have just got this, but it looks like a great text for gaining Windows Forms knowledge.
Programming C#Programming C# by Jesse Liberty
Buy used from: £2.66
O'Reilly books are generally excellent, this is no exception.
Programming ASP.NETProgramming ASP.NET by Jesse Liberty
Buy used from: £2.99
Another great O'Reily title, by the same author as Programming C#.
Design Patterns C# Workbook (Software Patterns)Design Patterns C# Workbook (Software Patterns) by Steven John Metsker
Buy new: £36.09 / Used from: £14.99
The GoF book translated into C#. Enough said.
Patterns of Enterprise Application Architecture (The Addison-Wesley Signature Series)Patterns of Enterprise Application Architecture (The Addison-Wesley Signature Series) by Martin Fowler
Buy new: £26.31 / Used from: £19.00
The title is a nightmare, the book is excellent.
The Mythical Man Month and Other Essays on Software EngineeringThe Mythical Man Month and Other Essays on Software Engineering by Frederick P. Brooks Jr.
Buy new: £15.96 / Used from: £10.39
You can't have a list of great software books without this.
Programming Pearls (ACM Press)Programming Pearls (ACM Press) by Jon Bentley
Buy new: £14.38 / Used from: £9.28
It's all about C programming - rewritting the solutions in C# is an excercise for the student:-)