Today's Microsoft Deal of the Day at http://shop.oreilly.com/product/9780735627048.do is CLR via C# price $23.99
I have read CLR via C# ISBN 978-0-7356-2704-8. Whilst it is quite correctly described by the publisher as a "Deep Dive", this is a
book that C# developers with 6-18 months plus experience ought to read.
Certainly any serious Microsoft programming shop ought to have a copy.
Even our experienced VB.NET brethren will benefit from reading this
book.
When I started programming 31 years ago I went through IBM 360
Orientation - this gave me an comprehension of what worked best at the
machine code level - this is the first book I have found that explains
the the working of the Dot Net framework to explain why particular
choices are good.