The underlying thinking throughout this book is on best practices. To make you think exactly what you want to do with Ajax and how to do it without pulling you're hair out.
Key Chapters encompass building the toolset you need, how to test effectively and how to debug properly (i.e. the foundations of good technique).
Most people will opt to use a framework to accomplish their needs and this book introduces some popular ones and arms you with the knowledge to make a qualified decision on which one to use. For the most up-to-date review of frameworks [...] is one of the best resources on the web.
Personally I would recommend Taconite (Ryan Asleson's Framework - one of the Authors) - [...] I combine this with an effects framework. MooFx is one I like.