"Boy, you're an alien,
Your touch so foreign,
It's supernatural, Extraterrestrial."
-Katy Perry, E.T.
I love that song. Why? Because I'm a sci-fi writer that's why; and what could be better than a sci-fi writer but a sci-fi romance writer? Okay I admit it, my previous work could be considered scant in the romance department, but I've since changed my ways. I've let my inner alien sex fiend persona out—well not completely, I still pretty much write sweet level romance but still there's that temptation when some good looking alien dude speeds by on his wing fighter. Why? What can it be that drives or draws us to someone or something not quite human?
"You're not like the others,
Once again Katy nails it. That "Different DNA" is where the attraction lies. It's exciting, it's thrilling, it's downright dangerous. Just as with the vampire/werewolf/daemon/shapshifter/zombie romantic obsession is based upon the forbidden and taboo, so too is the alien love connection. They may not give you roses on Valentine's Day but hey if you're dating an alien, you're not in it for the flowers. You're in it because you're bored with your earthly boyfriend and looking for something…different and an alien lover is about as different as you can get. They're sexy in a slightly kinky sort of way, odd but fun. And they drive a kickass muscle car! It can go from zero to light speed in less than a nanosecond, do space calisthenics, and still give you a luxury ride or a shaky thrill seeker kind of jaunt. Either way it's a trip.
Not only that, but when you're talking alien, there's that DNA thing again and whatever corresponding behavior that goes along with it. You don't know what he's going to do to you or how he's going to do it.
Decades ago, I read a wonderful book entitled The Girl with the Jade Green Eyes by John Boyd and it had a wonderfully different concept of love and sex. The beautiful alien woman castrated men for reproduction, but the human man she loved and who adored her received a different type of intercourse: she shared her mind, the most intimate communion she could give him, more important than sex and much more romantic as well. You got the idea of love, real love, deep and soul changing. It was an amazing moment when he realized that. After all these years I still remember that scene vividly.
Your alien lover, at least on paper at this point, can be evil, good, or just unfathomable in their dissimilarity to you, your heroine, and the reader. As long as he's sexy, well, I guess that's universal--literally.