Amazon Says E-Book Sales Outpace Hardcovers

In a statement Monday, Amazon's chief executive, Jeff Bezos, also countered the perception that sales of the company's Kindle e-reading device had suffered due to competition from other devices, such as Apple Inc.'s iPad.

He said the growth rate of Kindle device sales had "reached a tipping point," having tripled since the company lowered its price to $189 from $259 last month, following a similar move by competitor Barnes & Noble Inc. to cut the price on its Nook e-reader.

Amazon said Kindle device sales accelerated each month in the second quarter—both on a sequential month-over-month basis and on a year-over-year basis. But the statistics that Amazon shared were all relative—it didn't share actual sales figures. The company has never said how many Kindle devices or e-books it has sold.

Barnes & Noble, the nation's largest bookstore chain retailer, also has "seen a big uptick" since it cut the price of its Nook e-reader, a spokeswoman said.

Sony Corp., too, said that its sales of e-books were growing steadily, while second-quarter sales of its e-reading devices were about triple the level a year earlier.