Morningside Books is a bookstore on Broadway at 114th St. It replaced Papyrus, the former bookstore at this location. The bookstore has helpful staff and a nice atmosphere, but a limited selection. Few customers use this place in lieu of Labyrinth or the Columbia Bookstore, which is sad.
The store has a basement with even more books - most sci-fi, I think. Ask a staff member and they'll lead the way down there.