The reclusive manager of a large space-going junkyard discovers and re-activates a mothballed machine intelligence. He was lonely and wanted a friend--a companion. The ship was fine with that. It reasoned that being a human's friend was a great reason to exist.
A Best Circle of Hell Story Jahke is sitting "reading" in the library when two demons show up looking for fresh meat. And one of them takes a certain liking to their new human friend.
It becomes minor horned demon Sitka's job to take care of his new charge and introduce him to all the pleasures of demon life.
An envious friend pushes a beautiful wife towards infidelity, launching a once-happy couple on a dark, twisty ride. While they struggle to keep their marriage afloat, deep-seated insecurities, vanities, and traumas strike from every corner and crevice. Along the way, they gain unexpected emotional and sexual insights; but a sudden plunge casts them adrift, separately, towards nightmares, temptation, and domination. The tunnel becomes a crucible, which will either reforge or destroy them.
After the shattering experience the first time, Pam realizes that she truly is a submissive and posts the ad on Craig's list. I recommend that you read the other Pam stories first.
A humourous fantasy novel about time travel and some mild science fiction with special attention to their impact on human interactions. There are no descriptions of sex scenes as such but the last two chapters are quite erotic in an off-beat way.