Ken Henderson's latest book is out. We have a sample chapter on XML available (PDF, ~1MB). You can buy The Guru's Guide to SQL Server Architecture and Internals from Amazon. From the book: "The Guru's Guide to SQL Server Architecture is all about the internal pieces of SQL Server, the architecture of how they fit together, and the effect those have on performance and tuning issues. The book covers issues such as the new Notification Services which have not been covered in any other book, and also goes into more detail than any other book on the core SQL Server technologies. This new book will take its place next to his two previous books on the shelves of SQL Server developers and administrators everywhere."