Here's an excerpt from the book:
"Avatars are a new magic system for d20 games, drawn from Unknown Armies. In Unknown Armies, people can gain a measure of magical power by playing the role of an idea that has a strong representation in the collective consciousness of all living people. These ideas are called Archetypes, and those who follow them are called Avatars. The closer the Avatar cleaves to the bahaviors espoused by the Archetype, the more power the Avatar gains."
The section continues by delineating a new Avatar skill, symbols, taboos, godwalkers, ascension, & sample Archetypes. Another appendix adds new archetypes.
If you want, I'll sell you my copy for half the cover price $7, and I'll pay shipping (within the U.S.). It was sitting on my desk to trade for HARP, which is why I had it at hand to reply to your post. If you're interested, post here with your email address and we can work out payment (PayPal or money order).