Book: Inside SQL Server 2005 - The Storage Engine
In the first volume of the Inside SQL Server series for SQL Server 2005, Kalen Delaney again does a wonderful job of clearly describing many aspects of the system internals. Inside SQL Server 2005 - The Storage Engine is a must-have reference for anyone working with SQL Server 2005 at any depth. In this book, Kalen looks at how data is stored in SQL Server, particularly with reference to tables, indexes and locks. She also provdes good coverage of Row Versioning and Snapshot Isolation and shows many examples of using Dynamic Management Views (DMVs) to explore what's going on inside the database engine.
It's always good to be able to recommend a friend's book and this one is highly recommended!