Based on my own experience, I can safely say that every .NET developer who reads this will have at least one 'aha' moment and will be a better developer for it.
From the Foreword by Don Box
The popular C# programming language combines the high productivity of rapid application development languages with the raw power of C and C++. Now, C# 3.0 adds functional programming techniques and LINQ, Language INtegrated Query. The C# Programming Language, Third Edition, is the authoritative and annotated technical reference for C# 3.0.
Written by Anders Hejlsberg, the language's architect, and his colleagues, Mads Torgersen, Scott Wiltamuth, and Peter Golde, this volume has been completely updated and reorganized for C# 3.0. The book provides the complete specification of the language, along with descriptions, reference materials, code samples, and annotations from nine prominent C# gurus.
The many annotationsa new feature in this editionbring a depth and breadth of understanding rarely found in any programming book. As the main text of the book introduces the concepts of the C# language, cogent annotations explain why they are important, how they are used, how they relate to other languages, and even how they evolved.
This book is the definitive, must-have reference for any developer who wants to understand C#.