Looking for gothic vibes, taboo subjects maybe 60s/70s

I recently read Valley of the Dolls and Flowers in the attic.
I realize these are very different books but they are alike in many ways too. Mainly in how they explore darker themes and taboo subjects and also because of the time period they were written in.

Flowers in the attic – loved the immersive gothic feel, the dark romance aspect without it being an actual romance novel.

Valley of the dolls had me at the edge of my seat wondering which calamity would fall next. I like a bleak ending from time to time.

Are there any other hidden gems or iconic novels that might scratch this itch, maybe around similar era ?

Edit: no fantasy or YA please

Thank you!!