Digital books have outsold hardbacks for the first time at online retailer Amazon, the Financial Times reports.
The figures reveal the new importance of e-book sales, and the success of Amazon's Kindle e-reader.
The company said that, over the last three months, it has been selling 143 Kindle e-books for every 100 hardback books sold from its online store.
Last month, the number of e-book downloads increased to 180 for every 100 hardcover books.
In a statement, Amazon CEO Jeff Bezos, said: “Amazon.com customers now purchase more Kindle books than hardcover books - astonishing when you consider that we've been selling hardcover books for 15 years, and Kindle books for 33 months.”
The company also reported a rise in the sale of its Kindle e-book reader device following a price cut from $259 to $189.
Bezos said: "We've reached a tipping point with the new price of Kindle--the growth rate of Kindle device unit sales has tripled since we lowered the price from $259 to $189."