I would have to disagree with this and claim Patten Books as the best used bookstore in the area. Better selection, organization, and customer service makes it far better than any of its competition. Dunaway is alright, but I've yet to find anything that I went there to find and wasn't given much assistance in locating it either. All in all, I would say that Dunaway is at best number three behind Patten Books and The Book House.
Best Used Book Store St. Louis 2007 - Dunaway Books
To paraphrase Ernest Hemingway, Dunaway Books is a clean, well-lighted place. One that invites a Saturday afternoon's worth of perusal and page flipping. It's important to have the right kind of approach upon entering a used book store Dunaway may not have the exact book that you're looking for, but once you poke around the tall wooden stacks inside the South Grand storefront, chances are you'll find some other gem. The tomes are organized not just by basic "fiction" and "nonfiction" tags, but by a rainbow of genres: Read up on the Battle of Antietam in the Civil War section or locate your inner pagan in the Mysticism, Occult & Folk Lore shelf.