From Slashdot.org:

The U.S. publishing industry is driven by celebrity authors and repeat bestsellers, according to testimony from a blocked merger between Penguin Random House and Simon & Schuster. Only 50 authors sell over 500,000 copies annually, with 96% of books selling under 1,000 copies. Publishing houses spend most of their advance money on celebrity books, which along with backlist titles like The Bible, account for the bulk of their revenue and fund less commercially successful books.