I mean Nivens ringworld was basically a freeuse sexual fantasy/immortality fantasy thinly disguised as science fiction. Pretty much all science fiction from 1960 to 1990 was about weird sexual taboos with aliens.
God damnit. There's a book I read in high school about a Lion-Race Alien that is a member of the praetorian guard for this evil emperor guy. He ends up falling in love with the emperor's newest concubine, an alien lady from a water-world where you all just walk around nude because you only think you're naked when you're not covered in water. And then, when the emperor does some sicko sex-pest shit, he ends up leading a revolt that brings down the kingdom.
It was so fucking horny. Like, crazy horny. I cannot remember the name of the book. Something that sounded like Debt of Honor or Honor Guard or .... something with Honor in it.
Grey aliens are the immortal enemies of the cat furry people of Chan.
This looks like a book I'd find on a shelf in middle school and read while I was supposed to be studying math or whatever