• The Pragmatic Programmer: From Journeyman to Master by Andy Hunt and Dave Thomas
• Agile Project Management: Creating Innovative Products by Jim Highsmith
• Extreme Programming Explained: Embrace Change (2nd Edition) by Kent Beck
• Extreme Programming Pocket Guide by chromatic

Test-driven Development, Unit Testing & Refactoring

• Working Effectively with Legacy Code by Michael Feathers
• Refactoring: Improving the Design of Existing Code by Martin Fowler
• Pragmatic Unit Testing in C# with NUnit by Andrew Hunt and Dave Thomas
• Test Driven Development: By Example by Kent Beck
• Test-Driven Development in Microsoft .NET by James W. Newkirk and Alexei A. Vorontsov

Architecture, Design and Patterns

• Design Patterns: Elements of Reusable Object-Oriented Software by Erich Gamma, Richard Helm, Ralph Johnson, John Vlissides
• Patterns of Enterprise Application Architecture by Martin Fowler
• Enterprise Integration Patterns: Designing, Building, and Deploying Messaging Solutions by Gregor Hohpe and Bobby Woolf

.NET, C# and Related Topics

• .NET Framework Standard Library Annotated Reference, Volume 1: Base Class Library and Extended Numerics Library by Brad Abrams
• .NET Framework Standard Library Annotated Reference, Volume 2: Networking Library, Reflection Library, and XML Library by Brad Abrams and Tamara Abrams
• Framework Design Guidelines: Conventions, Idioms, and Patterns for Reusable .NET Libraries by by Krzysztof Cwalina and Brad Abrams
• Customizing the Microsoft .NET Framework Common Language Runtime by Steven Pratschner