Sometimes, The Long Tail isn't there
Here's what half the rack looked like.
Now, assuming that they are rational businessfolk, why would they use this very limited space to show us lots and lots and lots of copies of just three books? After all, they get restocked at least twice a day, so it's not to avoid an out of stock situation. The Long Tail would tell us that if they converted these three titles into, say, 50, they'd sell more.
I think I know the answer. People are more likely to buy a book (as opposed to buying nothing) if they think everyone else is reading it. And a great way to communicate that fact is with a display like this one.
Link: The Long Tail.