The rise of the romantic robot
Whether robots could one day think for themselves and the how this would affect humans' relationships with them is a common subject in science fiction. However, novelists are increasingly investigating another burning issue: could robots love a human?
Imagine a Venn Diagram with one circle representing the dark steeliness of humanoid robots and the other the flowery soft-focus pink of a Mills & Boon romance.
What would happen where the circles cross?
Only a few authors have braved an area that is almost literally a no-man's land, as in these books the stereotypical attractive male has typically been actively supplanted by a hunk of metal.
While the idea of robots and humans in a sexual encounter has been slithering around the underbelly of science fiction since the liberated 1960s, the addition of female-audience focused erotic romance is relatively new.
In fact Electra Shepherd, from Reading, is one of only a handful of published authors of the genre known as robot erotica.
Her novel Love Machine is the first in the Body Electric series and revolves around the love affair between a "good-time girl" and the house robot her late father invented.
"Blue's touch was pleasant," one passage reads. "It lingered there on her thigh as if he was getting her used to the feel of his synthetic skin. She pictured it, bright electric blue against the tanned flesh of her leg."
The pair end up falling in love and driving off into a romantic future.
"I was between books," explains Ms Shepherd. "I didn't have a contract and I just wanted to write something for fun.
"I thought 'what could be the most fun thing that I could possibly write' - and for some reason it was sex with a robot."
The reason, perhaps, this genre has chimed enough with our society to lift it up from the murkier depths of erotica is the prevalence of human-like robots in our collective psyche.
For example, the series Humans broadcast on Channel 4 about the Hawkins family and their female "synth" robot Anita, who ends up having sex with the father, has been hailed as the channel's most popular drama in 20 years.
And finding humanised robots attractive is more common than we at first may think.
"I've always loved the Terminator movies," says Ms Shepherd. "I think the Terminator is quite sexy - and I love Data from Star Trek and Michael Fassbender in Prometheus, and then there is Jude Law who is the robot gigolo in AI."
One of Ms Shepherd's readers Elizabeth Mason, a 51-year-old woman from New York, says the idea of erotic robots is really only a small leap from the now globally popular Twilight Saga series, where a girl has a romance with a vampire.
"It's the idea of the 'other'," she says.
"It responds to something deeply primitive in humans, something that we have repressed as we have evolved over the centuries.
"It's also kind of a taboo, but not a taboo that is illegal.
"People want something a little different from the tried and true."
Dr Adam Roberts, literary academic at University of London's Royal Holloway College and author of The History of Science Fiction, thinks there is also the aspect of "eroticising the machine".
"Shiny chrome, smooth gleaming surfaces, its machine-tooled curves and the feel of it," he says.
"This is connected with the way cars, say, become eroticised in culture more generally.
"In this sense the key thing is the machinic quality of the erotic experience: the way, for instance, machines can go on and on without tiring."
Another aspect he says is about "control".
"The crucial thing here is that a robot, or an android, is programmable, under one's command, can be made to do what ever one likes."
Erotic fantasies aside, Ms Shepherd, a former Mills and Boon author, says robot erotica is not all that different from your typical romance novel blueprint.
"The hero was the 'other'. He was always this alpha male, this super masculine billionaire and he was always from a different world than her, and it was this difference and his hyper-masculinity that made him so attractive.
"And the robot porn actually plays into that quite a bit. He's a different species so he's exotic."
These authors are keen on injecting the Mills & Boon-style romance into what has traditionally been a more threatening storyline of non-human betraying the human.
Across TV, film and novels machines end up turning against humans, from Hal in 2001: A Space Odyssey to 2015 film Ex Machina.
Bucking this storyline is author Gena Showalter, who has penned the Alien Huntress series, where an X-Files-type female character is lured into the arms of a dangerous but attractive alien.
Ms Showalter, who is on the New York Times best seller list and has sold six million copies of her books, says that underlying the subject of alien romance is raw human feeling.
"For me, it's never about the eroticism of the story but about the emotion driving the characters," she says.
"In the real world, everyone searches for love. In the books I write, I draw from that. Whether the character is an otherworlder, an immortal, half robot or a spirit-zombie slayer."
She adds the appeal for her readers is also the "potential for danger" as well as the "allure of becoming the lifeline the non-human needs to assimilate in our world".
So robot erotica, which on the surface may appear as a superficial bit of fun, appears to encompass a whole gamut of human desires. The attraction of the exotic "other", the excitement of danger and control, as well as the egotistical curiosity of humanising a machine so that it thinks and feels like we do.
Humanoid robots have been pervading science fiction for decades - such as in Fritz Lang's 1927 film Metropolis, or Isaac Asimov's I, Robot stories.
But this romanticised relationship between human and robot holds up a mirror to a society that is developing not just a metal humanoid with similar traits, but a robot that looks and acts human - such as those designed in Japan.
Ms Shepherd says it is also indicative of a current need for escapism: "I think especially in times of economic downturn, when times are tough, people like to read escapist stuff that is completely different from their normal life.
"If you look at the biggest book, 50 Shades Of Gray, it is that move towards erotic fantasy.
"Science fiction erotica is that step further".