This web site is an informal resource for the book: Richard A. Bartle, Designing Virtual Worlds. Indianapolis, New Riders, 2003. The rights to the book have been kindly reverted to me by the publishers, so I'm pleased to be able to provide it for you as a free download here. The formatting isn't as good as that of the published version, but hey, free is free!
I assume throughout that you've actually read the book. If you haven't, you may still find things of interest; serendipity is one of the good things about the Internet, after all. Don't necessarily get your hopes up, though...
If you haven't read the book but my attempts to embarrass you into doing so are working, you can buy it from (among other places) amazon.com and amazon.co.uk.
Disclaimer: although the good people at New Riders are responsible for the look, feel and design style of Designing Virtual Worlds itself, this web site is all my doing. Don't harp on at them if you find anything here that disagrees with you - it's not their fault.