If you take Ajax in Action as a more or less introductory tutorial you won't be disappointed. From the current crop of books -- as far as I know them! -- it appears the most thorough one.
That said, there are a lot of things still missing. I surely hope that publishers don't flood the market with ever more introductions and really advanced books start to appear soon. Topics that I'd like to see covered are
Test-driven development. This is already pretty straightforward for computational code. It is hard for code that interacts with a user or a server (impossible to do cross-browser?). Error handling. CSS layout for web-based applications. CSS mostly caters to the page design community; coaxing it into service for applications is no pleasure. Ceterum censeo, fixed pixel layouts are evil. Client-side architecture. Beyond saying "use MVC", that is.