I think their small size and specificity (and given the fact that a large majority of what they have is low-margin paperback fiction) is probably what makes it

I think their small size and specificity (and given the fact that a large majority of what they have is low-margin paperback fiction) is probably what makes it really hard to be viable, since there's no real way to ratchet up volume. The counter example is Green Apple Books, which seems to be doing well across two geographical locations in less populated areas of the city.