Amazon.com is now selling more Kindle books than paperbacks and hardbacks combined, with its UK business shifting twice as many e-books as hardbacks.

Gordon Willoughby, the European director for Kindle, called the UK rate of Kindle purchases "truly astonishing" considering the company has been selling hardbacks for 13 years, and Kindle books for nine months. Since 1st April 2011, for every 100 hardcover books Amazon.co.uk has sold, it has sold 242 Kindle books. The figure excludes free Kindle books but includes hardcover sales even if there is no equivalent Kindle edition.

Founder and c.e.o Jeff Bezos said the American company "never expected" Kindle books would outsell both paper and hardback covers together as quickly as it has. Amazon.com has sold three times as many Kindle books so far this year as it did during the same period in 2010. Bezos said: "Customers are now choosing Kindle books more often than print books. We had high hopes that this would happen eventually, but we never imagined it would happen this quickly—we've been selling print books for 15 years and Kindle books for less than four years."