XML Family of Specifications, by Kenneth B. Sall
This book is fairly large (approx. 1200 pages) and contains very good information on the design of XML in general. It covers DOM parsing, as well as SAX; includes several chapters devoted to design of parsers (mostly in Java, but applies to any language). Also covers DTDs, Schemas, XSLT, XPath, and more. Check out the Table of Contents at Amazon to see everything else covered. The book is slightly out-dated, and mostly is only missing new features to the XML family languages, but includes extensive coverage of the foundation. Highly recommended. I used this book when first starting to use XML/XSLT and is definitely for developers/programmers.
p.s. I spent 20 minutes trying to figure out how to get the book image to display and failed.