Harry Connolly is interesting about cover art, sub-genres, and pinning down what is "real" literature.
He posts three covers, one of which is to The Postman Always Rings Twice, which sits on literature lists, as the other two examples very plainly aren't. I've always thought of that novel as unexamined male gaze trash, tightly written trash, but trash just the same. However, it's been made into film several times, sits on best of lists (written by men), etc etc. Did the original publisher put it out as literature or trash?
Watching various works jink back and forth from literature to trash and back again can be as puzzling as decoding cover art.