Jaime Christley was working at a Barnes & Noble in New York when people started buying the retailer’s glossy white e-reader. It wasn’t long before he found himself appealed to for routine tech support: batteries weren’t charging, operating systems needed updating, touchscreens were on the fritz.

You can’t repair an e-reader without catching a glimpse of its digital library. And quite often what Christley saw took him by surprise: his customers were into porn.

Few benefits of the e-reader are as attractive as the privacy it inherently affords. Christley and his colleagues may enjoy a peek at the troubleshooting stage, but in public the anonymity is ironclad: you could be reading hardcore BDSM erotica on your Kindle or Kobo, but to your fellow commuters you might as well be poring over PG Wodehouse.

For those shy or easily embarrassed, that sense of confidentiality is liberating.

An erotica publication geared towards the male market. Photograph: Ellora's Cave

Fifteen years ago, Tina Engler started writing books about sex. She was rejected by every publisher she submitted to. They all echoed the same refrain: women don’t want to read about sex.

She wasn’t so sure. A lot of her friends, she felt, would prefer a romance that didn’t simply end with a chaste kiss and nothing more. So she began to publish erotica on her own, under the banner of Ellora’s Cave. It’s since become one of the most prominent purveyors of erotica on the market.

Raelene Gorlinsky, its publisher, credits the rise of the e-reader with the company’s early success. “Erotica,” she explains, “was around long before Ellora’s Cave, but it certainly wasn’t something you could buy at your local bookstore, because everybody looked down on it.”

The launch of Amazon’s Kindle in 2007 marked the epoch of e-reading, and, according to Gorlinsky, that’s when erotic romance took off. Ellora’s Cave, like most publishers of erotica, is a “digital-first publisher”, meaning all of their titles are introduced to the market as ebooks with the possibility of a paperback down the line.

The print titles, Gorlinsky says, are put out mainly to please the authors. Hardly anyone buys erotica in print.

Some readers aren’t necessarily ashamed of their interest, but, Gorlinsky says, “it’s just so much easier not to be challenged about it”. Despite its enormous popularity, erotic romance is still plagued by ridicule and mocking preconceptions.

Emily Veinglory, an author of erotic romance who maintains a blog about the industry, believes that erotica fans gravitating to e-readers was also “just a function of necessity”.

“Traditional publishing,” she says, “simply would not meet this market.”

The kinds of trumped-up romance novels you see on the shelf at Barnes & Noble are meager things indeed to the savvy reader. “When I read a Harlequin Blaze” – the well-known publisher’s “sexiest romance series”, according to their website – “I think: Oh, please. That’s their idea of erotic fiction? It doesn’t scratch the surface of what erotic ebooks are willing to offer you. You just can’t get these things in print.”

Erotic ebooks are often as explicit as pornography. And, like pornography, erotic ebooks can be divided into a staggering number of subgenres, catering to any conceivable taste.

“Readers follow the tropes,” Veinglory explains. “There are particular things that people will what they call ‘auto-buy’. If you write one of them, they will buy it.” Gay vampires, bisexual cowboys, 18th century transgender pirates: the list goes on.

Erotica fans are voracious readers, and, happily, erotica novelists are prolific writers. And the latter has to serve quite a number of very peculiar and precise demands. “Let’s say you write threesomes,” Veinglory offers. “There are people who will only read a threesome if there’s two men and one woman but the two men are not gay.”

Photograph: Ellora's Cave

And if you write 50 books of that kind and suddenly throw a curveball in your next volume? The readers will revolt. “This is their candy bar. This is their thing. Some people come home and have a glass of scotch. There are very particular buttons they want pushed, and if you push them, they’ll buy it.”

Gay male erotica is among the most popular categories of erotic fiction – though not, surprisingly enough, with gay men. “When I first started I wrote mostly gay material,” Veinglory reflects. “Ellora’s Cave did not take gay male romance because they said that their customers were mainly women. They had no idea that women love this stuff.”

They do have a line geared toward male readers, EC For Men, but Gorlinsky admits they were shocked to find that even these “were extremely popular with women”.

“We designed the line to try to get more male readers,” she says. “But apparently a lot of the readers end up being women anyway. I’m not sure why. Maybe they’re trying to figure out what men like.”

Erotic ebooks are helping people understand that “sex is good and pornography is not evil,” Veinglory says. “You can read about it, you can write about it, you can be interested in it, you can have fantasies about being tied up without losing your feminist card – or without losing your god-fearing woman card.” Anything that can permit people to accept pleasure on their own terms is a good thing.

“A lot of people thought their dirty little secret of what they wanted to read made them a freak,” Veinglory says. “Then the internet showed them that there are a million freaks out there. Whatever you are into, there’s a whole lot of other people who are into that.”

