I'm not a market genius, but I do know enough about human nature to tell you if you keep repeating the same thing over and over again people will stop listening. When the same types of books and mostly the same dozen writers get prime shelf space what's the point of going to the store? If I know I'm going to see the latest Dan Brown, Steven King and Twilight novels touted as "the best of fiction" when a) I have read them 2) I don't like them at all d) I've got no interest in those particular cookie cutter books, I'm unlikely as all hell to pay any attention to the marketing. When dozens, and dozens of new books in whatever area's i do read come out and I still see a "best seller" from four months ago listed as a "New Release" and nine of them on the shelves but can't find a copy of a book due out now or even last month by someone not in the anointed roll, what is my incentive to shop in a store when there are a dozen and a half websites I can name where I can find those books?
Further while I understand that micromanaging a chain of thousands of stores would be all but impossible, having the exact same selection in Denver, CO and Portsmouth, NH might work for big box department chains, entertainment items are not approached by the buying public the same way underwear, baby formula, and name brand motor oil are. Demographics dictate consumption. Again Demographics dictate consumption. A state like Massachusetts with a very high number of college degrees is going to have numbers different in some categories than a state with a very low high school graduation rate. Alaska, is probably going to sell a higher percentage of products aimed at men, Florida and Arizona will almost certainly sell more books aimed at older people than states which are on average younger. And even within states you're going to see differences. College towns will have different trends and sell more textbooks than farm towns and bedroom communities.
Of course you'd never know this to walk into a B&N store. I've been to several up and down the east coast, and points further west. The music stores have the same ratio of Sheyrl Crow to the J Giles Band and Coleman Hawkins in Saugus Ma and Richmond Va, Eminem and Enya get the same space in Portsmouth NH and San Diego CA, and numerous authors who visit conventions in Ryebrook NY, Boston Ma, or Chattanooga TN, are left entirely off the shelves because there's no checkbox on the order forms for "hey the author was here it might just possibly have left some residual interest". Also for the few stores that have readers groups, there's no shelf space or signage for "local readers like" and an automatic order of those books, sequels and other books by the same authors.
So the short answer is: try harder.