Sales of e-books may have already overtaken those of hardback in 2011 by volume, but it will take until 2014 for actual sales revenue to catch up, according to one forecaster.

UK e-book sales revenue will overtake hardbacks in 2014 and close in on paperbacks by 2016, an Oliver & Ohlbaum (O&O) forecast presented to London Book Fair’s Digital Minds conference showed.

Amazon and Waterstones reported e-book sales overtook hardbacks by volume last year. The lag indicates the lower prices that digital content can fetch compared with physical counterparts.

“While current publisher margins are higher on e-books than physical books, average retail prices are lower,” O&O said.

The analyst house reckons a quarter of the UK population will regularly buy e-books by 2017 – that is 40 percent of all regular book-buyers.

All of that will push total UK book sales by volume up 8.5 percent by 2017, O&O reckons. But, thanks to that dimes-for-dollars challenge, retail value will dip by 10 percent over the same period.

O&O thinks half of books, regardless of format, will be sold online by 2015.

Meanwhile, Sony’s Reder Store e-book store, first unveiled in the U.S. in 2006, finally rolled out in the UK today, despite Sony having earlier committed to an October 2011 launch.

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