True to its name, this enormous Southside emporium of used books and music is the largest independent bookstore in Pittsburgh. The selection is curated, so you don't have to sift through shelves of schlock. This spot is a nice node for literary and musical culture-vultures, and is known to host writer's workshops.
There are other locations downtown and in Squirrel Hill. Note that the store closes Friday evening and all day Saturday in observance of the Jewish Sabbath.