Flush with the success of Fifty Shades of Grey, erotic literature is increasingly finding ardent fans among women seduced by the discretion afforded by e-books, publishers say.
The Perfect Submissive, Body Temperature And Rising and Dark Desires are just three titles published by British specialist publisher Xcite that leave little room for doubt over their content.
The books were unashamedly on display in the bustling corridors of the Frankfurt Book Fair, the world's biggest publishing event due to close Sunday, and are enjoying a boost thanks to the advent of the electronic book.
The erotic book is "an ideal genre for e-books", said Peter Ferris, non-executive director at Accent Press, whose imprint Xcite is the biggest British erotica publisher.
"Print book sales were starting to decline. Getting into the major book stores was difficult. Some stores are not happy to take them and the buyers are very hard to reach," he said.
And then Fifty Shades of Grey came along.
The 2011 erotic novel by British author EL James was the first part of a trilogy about a relationship between a college graduate and a young business magnate and has sold tens of millions of copies worldwide.
Since Fifty Shades of Grey started to top the bestseller lists, e-book sales have undergone "a very large increase" and made erotic literature more publicly acceptable, Ferris said.
"It raised the attention level or people's awareness of erotica. It made it more mainstream, more acceptable. It's no longer something you don't talk about, it's in the bestsellers' charts," he said.
Xcite now expects its e-book sales to be three times higher than printed book sales this year.
Germany's Jolanta Gatzanis, editor in charge of erotic literature at the publishing house that bears her name, says e-books have been flying off the digital shelves, and without having to be promoted.
"We sold a lot of electronic books this year without doing much publicity. That really surprised us," she said.
In Germany, no fewer than 4000 erotic reference books for adults are currently available on the internet, albeit of varying quality, says Roman Jansen-Winkeln, of Satzweiss, a services' provider for publishers and authors.
"There are some of good quality but a huge number of books of very mediocre quality which would have never been printed. A bit like for thrillers. But if a bad thriller can still be quite amusing, there's nothing worse than bad erotic literature," he said.
This genre of books is predominantly read by women, the publishers agreed. Jansen-Winkeln said he believed more than 80 per cent of readers of erotic literature were female.
"We don't actually see the gender of the customer but... the writing itself is aimed at women, and it's written mostly by female authors who are writing for women," said Ferris, of Accent Press which also publishes thrillers and cook books.
Discretion could be the key.
With no cover on display, an e-reading device such as a Kindle makes the literature anonymous to the outside world, Giada Armani, who heads up erotic literature publishing house Giadas.
"I think that women have always wanted to read erotic literature. But what woman brandishes an erotic book in the underground or at work whose cover displays the silhouette of a naked man?" she said.
And, as Ferris pointed out, the reader can also retain their own anonymity by downloading e-books without having to go into a shop.
"You can even erase it once you're finished so nobody knows what you've been reading," he said.