The balance of power seems to have shifted in the favour of Macmillan as online retailer Amazon. com acceded to the request of the former to sell its books for as much as $14.99, higher than the $9.99 it charges for most best-sellers and new releases.

Amazon said it was capitulating because Macmillan has "a monopoly over their own titles." Shares of Amazon. com Inc - largest internet retailer, fell the most in more than six months, sparking concern that it's losing its pricing advantage.

Amazon. com has sought to hold down the price of the most popular e-books, aiming to make its Kindle e-reader more appealing. As rivals to the Kindle emerge, including the recent Apple Inc.'s iPad and the Skiff Reader that was showcased at the CES 2010 last month, publishers have more power to influence the price of books.

"Publishers weren't happy with the Kindle pricing before, and the release of the iPad has accelerated their displeasure," said Carl Howe, an analyst with Boston-based Yankee Group.