oh, you mean fifty shade of- blah!!
i know a novel where hardcore rape / abuse / slave is pretty common in the premise... i dropped it long time a go but I believe it has name like "god & devil world or realm something", i can't remember.
the synopsis is a chinese university dude in a modern world where suddenly zombie apocalypse happen. he got a skill to summon some skeleton so he can survive zombie horde > getting stronger > establish camp etc .
then it quickly become: getting strong > adventure > sex > adventure > sex. lmao