Our new book, Professional SQL Server 2008 Internals and Troubleshooting, will be shipping soon! Order now! :-) Christian Bolton, Justin Langford, Brent Ozar, and James Rowland-Jones have each written several chapters in this book. Steven Wort, Jonathan Kehayias and I each contributed a chapter as well. The 1st half of the book introduces you to how things work within SQL Server at a level that will make it easier to understand the rest of the book. The 2nd half of the book focuses on troubleshooting common SQL Server problems.
Download the first chapter and find out more about the book here: http://sqlservertroubleshooting.com/.