As a kid, I was very creeped out by this Bantam cover of Miller’s A Canticle for Leibowitz when I found it on my parents’ bookshelf. I was already reading sf, but somehow that didn’t seem to apply to this book (which was carefully not packaged as sf in its first few paperback editions). The monkish figure in the foreground seemed deeply sinister to me. I could hear him snarling whenever I looked at the cover.
I finally picked it up and read it in a later edition with a gorgeous coppery-gold cover painting by Lou Feck, at which point it went straight onto my “always reread” list. (Wish I still had that copy; later printings masked most of the image with a white frame.)
I don’t remember ever discussing the book with either of my parents, which seems like a missed opportunity in retrospect. They weren’t sf/f fans, but they were very bookish people and very Catholic people; I’m sure they’d’ve had interesting things to say about it.
If they read it, of course. In those days, many a bookshelf was littered with bestsellers that were never read. But my parents’ libraries, like that of the younger Gordian, were designed for use rather than ostentation.