Unfortunately the Guides and Books links aren't much use. Instead, have a look at the "small talks" series on his blog http://blog.redline.st/category/series/
We also did a presentation at Smalltalk Solutions a couple months ago.. http://vimeo.com/22084832 which has some good background info from a 'what are they trying to accomplish angle'. Its geared very much towards a smalltalk audience but others can get stuff out of it.
There is also the mailing list where we'd be happy to answer any questions.