There are a number of book and literary festivals held in San Francisco each year; here's a list of some of them:
October 10-18th. "Originally hatched over beers at the Edinburgh Castle pub in 1999...Now grown to the largest independent literary festival on the West Coast, Litquake continues its mission as a nine-day literary spectacle for booklovers, complete with cutting-edge panel discussions, unique cross-media events, and hundreds of readings."
San Francisco Zine Fest
August 30-31st. "A free, annual celebration of small-press publishing, from zines and comics to art books and beyond. The SF Zine Fest serves as a vital showcase of the diversity, creativity, and ongoing exuberance of the small press movement."