I just finished reading Professional Ajax, the new book by Nicolas Zakas, Jeremy McPeak, and Joe Fawcett.

"Professional Ajax" shoots from the hip. Go ahead, scour the web. Find every forum, article, or review about Ajax that allows users to post comments. You'll find a common complaint: "We've been doing that for years, we don't need a fancy new name." These guys understand this comment. They know what they're doing here, and they've got the battle scars to prove it. Call it what you want: Ajax, Web 2.0, or just business as usual, these authors know how to get the job done.

You won't find oversimplifications here: the authors don't skimp on details as they describe what goes into Ajax applications and show you how to build your own. The book concludes with a large and lovely guide through the process of developing a realistic Ajax-based email client similar to Gmail.

This is a nice pragmatic guide to coming up to speed with what's happening in interactive Web application development. You won't go wrong with this book.