The sole in-depth example is a shopping cart application, which is fine, but plenty of simple ready-to-run examples that show various aspects of working with AJAX would help much more. Other examples use outdated techniques like XML islands and hidden frames, which muddles the picture further.
The authors' style of writing also gets in the way. It's probably supposed to be easy-going, but includes a stream of witty and self-deprecating remarks that detract from the content, and by the 10th repetition of "this is all mad-scientist stuff" this reviewer was yearning for some actual stuff, not fluff.
The chapters of the book that do talk about AJAX provide a decent introduction to the XMLHttpRequest object, and how to use it to transfer information back and forth from the server. It?s all bits and pieces, though, and no big picture is ever provided. Anyone who was inspired by Google Mail or Google Maps to build AJAX apps will not know where to start after reading this book.