I have to agree with Michael Hart on this one. The book isnt very good to be honest. It starts out ok, but somewhere it seems to lose its way. Perhaps just the few early chapters which ought to be relevent to 1.2, 1.3, 1.5 and 2.0, and talks about how the system works. (The book really only covers the early versions), and zimmer's document is up to date for 2.0 as I understand. Im really surprised too - considering the authors of the book wrote GEOS. Anyway, as soon as I get some time Ill get them (first couple of chapters) scanned.