Amazon.com says it is selling more electronic books than printed books, less than four years after it started selling e-books.
Since April 1, Amazon.com says it has sold 105 e-books for every 100 printed books, including printed books for which there is no electronic edition. The comparison excludes free e-books.
Printed books include both hardcover and paperback books. Amazon said in July that e-book sales had outstripped hardcover sales.
Amazon also says the latest and cheapest version of its Kindle e-book reading device is the best-seller of the line, five weeks after it was introduced. It costs 114 dollars (£73).