Many people see one advantage of an e-reader as its privacy - unlike with a physical book, nobody can see you're reading 50 Shades of Grey on the bus.
But many users of devices such as the Kobo or Amazon's Kindle might be surprised to discover that their reading habits are in fact being shared - and in some detail, at that.
Michael Tamblyn of Kobo, which supplies e-readers to WH Smith, John Lewis and Tesco, says in an interview with the Daily Mail that the device monitors reading patterns minutely.
The aim is to collect data that can be used to predict which books will sell well in the future.
"We're synchronising a bookmark constantly as you move along. That gives us insight into how you're engaging in the book that you're in... so if you have stayed up through the night and you can't put that book down, that helps us find other books from other people who have had that same kind of experience.
"When you think about the number of books people buy and don't finish, the 'other people who bought this also bought this [formula]' isn't that good a way to try to recommend a book."
Meanwhile, the Amazon Kindle and Barnes and Noble Nook do the same. They can even tell how far you've got through a particular book - so they'll know if you gave up on War and Peace halfway through.
"These companies have a heavy investment in your personal life in order to email you other product offerings or use your data as a bargaining chip in establishing relationships with international bookstores and distributors."
There are signs, though, that Brits are falling out of love with e-readers. Waterstones, for example, recently told the Financial Times that sales of the Kindle had 'disappeared'. And while figures from market researcher Neilsen show that UK readers spent £300 million on e-books in 2013, that pales into insignificance compared with the £2.2 billion we spent on physical books in the same time.
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