So, how did they get the books to stay in that shape? Glue or some sort of post drilled through the center of each? It would be a liability to simply use friction to keep them there--all a customer would have to do is pull out one to send the rest toppling down on his or her head. And to ruin perfectly good books just to have a covered walkway is a shame. (Unless they're not perfectly good books, in which case good riddance.)