J2EE Web Services: The Ultimate Guide by Richard Monson-Haefel, Addison-Wesley
The book builds from introductory concepts of XML and Schema into the fundamentals of SOAPand WSDL (critical to read if you are just getting started), from there comprehensive coverage of the key aspects of Web Services. The illustrations and diagrams are very clear and helpful in solidifying the concepts. I like the hierarchical layout of the book allowing one to select a concept to delve into one specific aspect. When using as a reference, you would go to the appropriate chapter and section and get a great in-depth amount of coverage of each topic.
Richard’s books always deliver complete information and this book is no exception. If you are doing or planning to do any web service work this book should be on your desk.