Because of SQL Server 2005′s support of XQuery, a lot of folks have been asking about good XQuery-specific books. I’ve found two excellent books, each with a different focus.
“XQuery From The Experts” is a compendium of essays by the folks in the W3C XQuery working group. It’s an excellent treatise of how XQuery is meant to work, the problems its meant to solve, and the details of implementation. Since most of the writers are also XQuery processor implementers, you’re getting the “inside story”. I especially like Jonathan Robie’s XQuery tutorial chapter and Michael Rys’ chapter on implementing an XML data type. Michael’s XML data type implementation theory is not identical to the SQL Server 2005 implementation (although he’s the PM for this feature), but its close enough in concept to make it a great read if you want to understand this feature.
If you’re more interested in XQuery from a user perspective, Michael Brundage’s “XQuery: The XML Query Language” is right up your alley. Michael covers the syntax and usage in depth, with lots of examples. The XQuery specs lack all but the most cursory examples (it’s not their charter) so Mr. Brundage’s book is a must. Although Michael works at Microsoft, his book doesn’t cover the System.Xml implementation in .NET 2.0, but the language as defined in the spec. So you’ll be doing deltas with the SQL Server 2005 or System.Xml implementations (which are closely aligned) in any case.
Remember that both books are based on a standard-in-progress, although now it’s close to done. Happy XQuery-ing.