I just finished Scott Davis and Tom Mars new book, JBoss at Work. He and his co-author do a brilliant job of taking a dauntingly large topic, an application server, and writing an engaging book about it. I particularly like their approach, which is very pragmatic: they take a web application that consists of static pages and gradually add more dynamic behavior, one step at a time. I think this is a particularly effective way of introducing a topic (I did the same thing with web frameworks in Art of Java Web Development because it addresses the whys as well as the hows).
My only complaint is one that Scott also laments: lack of testing code. But, I understand that the book would be much larger if they had incorporated testing. In that regard, they did the right thing: the book is about JBoss, not about testing in the J2EE space (a topic worthy of a large number of books all by itself). Kudos to Scott and Tom for a great book.