I have vague memories as a teenager reading The Night's Dawn books under the desk at school, getting really embarrassed by the multi-page hardcore sex scenes and the protagonist being, uh, a pretty bad person.
There's just something about Doorstop Sci-fi books that seem to lead their writers into trying their hand at fancy space smut.
It contrasted to Melanie Rawn's Dragon Prince series, which I read around the same time, where (IIRC) it's either wholesome romance or very obviously intended as something deeply unhealthy... although there was a lot of that!