According to event organizer, Deborah Porter, Boston, up until now, was the only major American city without a book fair.
This coming Saturday, October 24, from 10am-6pm, the Boston Book Festival will be taking over Copley Square. You can go to bostonbookfest.org to read up on all of the events and authors who will be present. You can also read the interview with Ms. Porter here, on bostonist.com.
It looks like a great festival, including appearances by John Hodgman (from the Daily Show and the Mac vs. PC commercials), Ken Burns, the well-known documentary film maker, and authors such as Anita Diamant (The Red Tent), Richard Russo (Empire Falls), and Ben Mezrich (The Accidental Billionaires).
There are also some really great events for kids and teens, which can be found here.
The entire schedule of events can be found here, and be sure to note that some events require tickets. Those events are, however, still completely free!