Amazon.co.uk has announced that Kindle books are outselling print, both paper and hardback, through the online retailer. The figure the company puts on the sales are 114 Kindle books to every 100 print books sold.

The Kindle was introduced to the UK in early 2010 and was quickly a hit, the biggest-selling product on the site by October 2010. Fast-forward two years and the success rolls on, with the Kindle being the ebook reader to beat.

However, the success of Kindle Books should be taken in context, because this announcement relates only to sales through Amazon.co.uk and doesn't take into account print books that may have been purchased elsewhere.

Amazon say Kindle owners are buying four times more books than they were previously, but again, this figure needs to be taken with a pinch of salt.

Kindle is a closed system, owners have no choice but to buy through the Kindle Store, so of course that's where sales get recorded. However, what this figure might reflect is that these sales have been taken from other booksellers, such as Waterstones or WHSmith.

Amazon has recently revealed that chick-flick-lit Fifty Shades of Grey has shot to the top of the sales charts, selling more than 2 million Kindle books in the past four months. 

Many have attributed this success to the Kindle's privacy – the lack of a book cover means no one knows what you're reading, making it ideal for racy literature.

But we're left wondering if these results are due to this huge bump in sales from EL James's Fifty Shades trilogy. Also within the top 10 authors on Kindle is self-publishing author Kerry Wilkinson, with 300,000 sales (spanning 2011-12), which perhaps gives a measure of the other author sales contributing to Kindle's success.

So it certainly sounds like good news for the adoption of ebooks, but we suspect there is a little more to the puzzle than currently revealed.