
This HaBO comes from Allison, who wants to find this romance:
I remember reading a book in ~1998 about a red-headed woman in her twenties. I think her face and waxy hair are on the cover.
She was a student in search of a famous painting for her degree. She went to a ~castle/older building (?) where she stumbled on a weird sex place with various characters having sex in various vignettes. There was an older-ish man (40s) who pretended to be a virgin to sleep with her.
She ended up liking a custodian/janitor and sleeping with him but he turned out to be owner of the castle and he had the painting she was searching for in his room.
Does anyone remember this?

The painting bit sounds kind of like Enchantment by Christina Skye, which I think did come out in 1998. I don’t remember anything about a weird sex place or a guy pretending to be a virgin, though. Good luck and I hope this helps!
Wowza. That’s some crazy. Hope you find it.
Commenting so I can read it too, when someone solves it
It’s The Red by Tiffany Reisz!
I thought the crazysauce plot sounded like something Black Lace would have published and that led me to Dark Obsession by Fredrica Alleyn.
Not sure if the plot fits perfectly, but the cover features a redhead with a lot of wavey hair. And a GR review references a plot twist at the end, which could be the reveal of the owner of the painting.
Blurb:
“Ambitious young interior designer Annabel Moss is delighted when a new assignment takes her to the country estate of Lord and Lady Corbett-Wynne. The grandeur of the house and the impeccable family credentials are a facade for shockingly salacious practices. Lord James, Lady Marina, their family, and their subservient staff maintain a veneer of respectability over some highly esoteric sexual practices.”
https://www.goodreads.com/book/show/3231143-dark-obsession