- Kindle books most popular format has announced that its customers are purchasing more Kindle books than all print formats.

Introduced in November 2007, Amazon's Kindle is now the most popular book format for its US customers. customers are now purchasing more Kindle books than hardcover and paperback books combined.  Three times as many Kindle books have been sold this year than in the same period in 2010.  Free Kindle books have been excluded from the growth rate figures. 

In the UK, the sales of Kindle books have overtaken the sales of hardcover books.  

Source: Amazon