Why Sainsbury's bought Amazon competitor

Ian Nicholson/PA Wire/Press Association Images

Sainsbury's has announced its purchase of a stake in an e-book website called Anobii from HMV for £1. The site is a competitor to Amazon, and while it sells books for iPads and smartphones, it doesn't sell them for Amazon's Kindle device.

So why did it make the purchase, and what does this mean for e-book buyers?