Rucker dubs chaotic -- "complicated but not random" -- systems 'gnarly' (from "a knot in the wood of a tree", by way of California surfer slang for "complicated surf conditions").
This book-and-disc package explains and implements various a-life programs, for you to play with, experiment with, and help develop your intuition about the behaviour of 'gnarly' systems.
But it all feels rather trivial and rushed -- not up to Rucker's usual standard at all.