From Publishers Weekly:
Whatever Hachette is paying James Patterson, it may not be enough. The prolific author placed six titles among the top 50 sellers, based on Nielsen BookScan sales data through December 16. Patterson helped Hachette place the most books on BookScan's top 50 list; its 11 bestsellers sold a total of 4.8 million copies. Although Scholastic had only three titles on the list, those three—including the year's top seller, Harry Potter and the Deathly Hallows—sold 8.6 million copies.
Simon & Schuster had eight titles among the top 50, led by The Secret; the company's bestsellers sold 6.6 million copies. Seven Penguin titles—selling a total 6.5 million copies—made the top 50. The country's largest trade publisher, Random House, also had seven titles (selling 3.2 million copies) among the top 50; its biggest bestseller, The Road, came in ninth place. The four HarperCollins books on the list totaled sales of 2.5 million copies.
BookScan captures approximately 70% of total book sales.