Mothra , 3 days ago

Maybe Ursula Le Guin? The left hand of darkness is quite thought provoking. People can switch sexes at will in that story. Yes, there is some mention of nudity and adult topics but I can’t recall a single sex scene. If this sounds too risky, try the wizard of Earthsea, which I found incredibly bland and super safe for work. It’s about as riské as Harry Potter 1. And is a short read too.

I think you should be safe with most classics, like the other comment said, Agatha Christie is a good choice… Though maybe not super progressive.