StoryBundle periodically bundles 5 drm-free indie books in a defined genre for sale with the purchaser setting the price. The current bundle consists of thrillers and mysteries. If you decide to pay $7 or more, you get another two books. It's a novel way to sell indie books.See: http://storybundle.com/
After the bundle deal is up, you can purchase the books individually with prices set by the authors. The thriller/mystery bundle is available for 7 more days.