Instant Messaging in Java, Iain Shigeoka, 2002.
This book is targeted primarily at intermediate developers, Jabber enthusiasts, and technical managers. Non-technical people who need to know about IM in general or Jabber in particular will gain the most insight from the first part of the book. The latter parts of the book contain many technical details and Java source code that you may find of lesser use if you are not a programmer.