It used to be that if a developer wanted to write an add-in for Visual Studio or extend the Shell, any technical resources were few and far between. That is slowly changing as new resources on MSDN, blogs, and in print continue to pop up. Wiley, via Wrox, recently released an entire book devoted to VSX, written by Keyvan Nayyeri. Keyvan was kind enough to have Wiley mail me a complementary copy of Professional Visual Studio Extensibility to read and review.
The book targets the mid-level to advanced .NET developer. I would not recommend it to those new to software development. This is due to the fact that VSX itself is not a simple subject. The first three chapters do provide an overview of Visual Studio, the .NET Framework and Visual Studio Extensibility for less experienced folks who are determined to tackle VSX.
The subsequent chapters cover topics such as writing, debugging and deploying add-ins, the Visual Studio Shell, and writing macros. Each topic is covered in enough detail to prepare the reader to extend Visual Studio in just about any way possible. The book contains enough screen shots, class diagrams, and code snippets to help the reader understand the topic at hand. Of course, all of the source code is available for download on wrox.com.
The books is well written and accurate. Kudos to both Cody Reichenau, the technical editor, and Keyvan. I absolutely recommend this book. It will be extremely useful to VSX developers, either as a guide to get up to speed quickly on a particular aspect of VSX or as a desktop reference, complementing the wealth of information available on the Visual Studio Extensibility Developer Center on MSDN.