Now Pimp My Novel takes a closer look at bestseller lists, including one tidbit that is a bit shocking, “For example: let's say Barrel O' Books maintains a store-wide "Top Ten" bestseller list, and they're overstocked on a particular title that isn't quite making that list. They may swap out the #10 title for the overstocked title, or may grant individual stores limited discretion when displaying the list, meaning it may differ slightly from location to location. (Book sales are surprisingly regionally varied in nature.) It's not exactly underhanded, since the action of adding the title to the list (and applying the appropriate discount, if applicable) will probably bump that title onto the list numbers-wise in short order. It is, however, something of a self-fulfilling prophecy.”
Read more here.