Amazon landmark for digital books

Sales of digital books for e-readers have surpassed hardbacks for the first time on Amazon, marking what the online retailer called a "tipping point" for book publishing.

For every 100 books Amazon shipped in hardback format in the past three months, it has sold 143 electronic titles to users of its Kindle e-reader, according to its founder, Jeff Bezos.

"Even while our hardcover sales continue to grow, the Kindle format has now overtaken the hardcover format," said Bezos. "Amazon 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."