Generally, the books I read have pretty uninteresting covers (well, at least to me). Recently, it's been mostly military history, political science, or economics, and those tend to have either nothing but a title on a single-color background or maybe some public-domain photograph slapped on the front for the military history stuff.

I have an art book or two, but that seems kind of like cheating. In terms of regular books...hmm.

I'd guess that the best ones are probably from fantasy books, and I haven't read much fantasy for quite a while.

tries to think though all of the fantasy books for one I liked

Well, going way back, the original Dragon of the Lost Sea cover. The hardback edition had a kinda Chinese ink painting-style image that spanned both the front and back. There was a later reprint that had cover art that I really disliked.

searches

https://lemmy.today/pictrs/image/146249e3-cede-4929-8961-45e5c6f9bf7d.jpeg

Not saying that I disliked the book, just that I liked the cover.