What's currently the most popular genre?

[Orrex]

I checked out a book sale at a local church the other day and was amazed to discover that what I thought was the main building was in fact just a heap of John Grisham novels. And then I came to the huge Clive Cussler monument, the Tammi Hoag gymnasium, and the Tom Clancy stronghold.

Honestly I'm not really familiar with these authors (or any of the others whose works were on display by the gross), but it got me thinking: Which is the best-selling genre right now?

It would seem that crime drama and similar suspense thrillers hold the prime spot, but these are also the best-represented in the secondary market, suggesting that their fans don't like them enough to hang onto them.

What are your thoughts?