Amazon has announced quite a milestone for its Kindle ebooks - they are outselling hardback books for the first time.

The online giant has revealed that for every 100 hardbacks that it currently sells, it sells 143 ebooks, and that for the last month there has been a big boom in sales where the ratio was more like 180 to 100.

Now this doesn't mean the end of the physical book by any stretch of the imagination - after all, Amazon isn't the only bookseller in the world - but it does highlight what is a massively expanding area.

It's not just the Kindle platform where ebooks are thriving - according to figures from the Association of American Publishers, ebook sales have quadrupled this year up until May throughout the market.

“This was a day that was going to come, a day that had to come”, said Mike Shatzkin, founder and chief executive of the Idea Logical Company who specialise in digital change. He also stated that he expects that fewer than a quarter of all books sold will be physical by 2020. 

The result is “astonishing when you consider that we’ve been selling hardcover books for 15 years, and Kindle books for 33 months”, said Amazon's chief executive, Jeffrey P. Bezos.

Amazon recently slashed the price of all its Kindle readers, and users can also get access to Kindle's ebook titles via apps on their iOS, BlackBerry or Android devices as well as on their desktops via Windows or Mac OS X.

Are you a Kindle fan? Have you gone the whole hog with some Kindle hardware or do you get your ebook fix on your mobile device? Let us know your Kindle habits using the comments below.