For those anxiously looking forward to Joshua Eichorn's "Understanding Ajax" book, there's a note on his blog you'll want to check out.
The lead story at ComputerWorld.com is an excerpt from my book Understanding AJAX. If you are thinking about buying the book, but needed more information to make a decision nows your chance.
The sample chapter is the first, teaching about the basics of Ajax - how its structured, what it does, even alternatives to it. You can also check out the table of contents and see what other topics are being covered.