The Encyclopedia Britannica has announced it is to stop publishing its print edition and will only be available digitally.
And erotic fiction is seeing good sales on the grounds that people can download e-books without anyone knowing what they're reading.
For example, a novel written by a British author EL James called 50 Shades of Grey has shot to the top of the US e-book chart.
Tom Tivnan, features editor for The Bookseller, told the Today programme's Evan Davis that no one has really been reading print reference books in the last 15 years, turning instead to the internet.
He said that genres such as erotica and romance have seen a shift of 40 to 50 percent to digital formats compared to just 12 percent in other genres.
"Mills and Boon are probably one of the savviest digital publishers in Britain", he added.
Rowan Pelling, former editor of Erotic Review and now a Telegraph columnist, said that she was not surprised at the success of EL James' book in the US because "every new media has really lent itself well to erotica".
She said that "women are more dishonest" about reading erotica so digital formats mean they can access it without people knowing.
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