The actual content of this book is 50% DHTML, 30% application design, and 20% AJAX. And by AJAX, I mean, something that actually involves asynchonous (or synchronous) communication with the server. It could be entitled "Head First DHTML with Ajax." The DHTML lessons are in DOM and javascript/json (of course.) The application design emphasizes separation of content from presentation from behavior. At my level of expertise, I learned more than I thought I would from the non-Ajax topics. I have not read any other book on Ajax, so maybe there just isn't too much to learn about AJAX, so the authors padded material with the 'interactive spirit of AJAX', i.e., DHTML.

I have read another Head First book, Design Patterns, so I anticipated a little fun. This book was not as fun. The word search puzzles have no value; you are not forced to remember what you've learned. I prefer the crosswords of the Design Patterns book.

The authors leave security considerations to the last chapter, where they tell you that you've been doing executing the less secure form of asynchronous communication for the previous 11 chapters. Read the whole book.

I didn't have PHP installed, and installing it was a chore. The book (also Head First/Oreilly websites) gives no clue as to how to install, and executing the first procedure I found online completely disabled my IIS 5.1 server(Window XP OS). There is no instruction in PHP despite the fact that all the async communications are with .php files.

You'll definitely want to hit the errata and forum pages online as there many errors, including plainly incorrect statements in big type.

I imagine that reading this book makes the reader almost dangerous, but you'll need to pick up PHP to really do some damage.