This manual has been available on this site since about 1996, with improvements taking place frequently. The current version has been published as a book of about 350 pages by Cambridge University Press. By agreement with the Press, however, it will remain posted on this web site. Many improvements in the current version over previous ones are due to the (anonymous) referees of the Press, whom I wish to thank heartily. I also wish to thank Lauren Cowles, of the New York office of the Press, for much help with preparing the original version for publication. The paper edition appears also in Duotone red and black. For information on obtaining the paper edition, take a look at the Cambridge Press catalogue . From January 1, 2004 on, no changes except simple error corrections will be made to the main body of the text here --- at least for a while. Corrections to both paper and web editions will be found below. I am grateful to all those who have pointed out errors or lacunae in older versions of this manual, and I hope readers will continue to send me mail about what they find - both good and bad - at cass@math.ubc.ca .