The company said that in the last three months it had sold 143 e-books for every hardcover book. In the last month this had risen to 180 e-books for every hundred hardbacks.
"That is dramatic evidence of how powerful the e-book is now," Citigroup analyst Mark Mahaney told the Wall Street Journal.
"What the iPad and other book reading devices have done is just raise the overall e-book market and Amazon is extremely well positioned to take advantage of it."
These results will have huge effect on the publishing industry since hardcover books are traditionally the area in which the most profit is made in publishing.
Amazon also reported that sales of the Kindle had mushroomed since the most recent price cut.
"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," Amazon boss Jeff Bezos reportedly said.