I’ve been slowly working through the draft version, and being new to Agile development, find it extremely helpful. It’s supposed to be released in 2007, but there are quite a few sections that aren’t finalized yet, so I don’t know if he’ll make it.
It can be found at The Art of Agile Development
P.S. If you want a copy of the site as it exists, I’ve been using the Scrapbook plug-in in Firefox.