Professional Ajax by Jeremy Mcpeak, Joe Fawcett, Nicholas C. Zakas (2006, Paperback)

I am admittedly a fan of Wrox Press. Their books are consistently fantastic. Professional Ajax covers a lot of ground and does so fairly quickly. Having a personal minimal amount of Javascript experience I found myself having to "cross-educate" myself as I progressed through the book. Having said that I would strongly recommend that a reader either have previous javascript experience or read a good Javascript book first. You'll be glad that you did, but the publisher makes no qualms about this (It is a "Professional" book not a beginners book - that version is expected out in August of this year) and even states that previous Javascript experience is necessary.

If you are looking for a good nuts and bolts book that covers advanced options (XML/JSON/XSLT/ETC) this is a great book. I have previously invested in an ajax book from another publishing house (remaining unnamed) and I found that once again I prefer the WROX book.

The bottom line is that if you like the Wrox books this will be a good one for you, and if you don’t like this particular publishing house then go get a kiddie book from somewhere else.