Since we’re sort of expanding science fiction to include fantasy / ghost stories, etc.
You’ve already mentioned Tolkien.
“Detective of Dreams” by Wolfe is very good, both disturbing and comforting.
Russell Kirk’s “The Peculiar Demesne of Archbishop Gerontion”–really spooky, really Catholic. “He genuflected before the crucified figure on the wall.”
Was M.R. James Catholic? If not, he was at least definitely “High Church.” ANYTHING ANYTHING ANYTHING by M.R. James. The greatest at ghost stories, ever, anywhere.
This guy’s not Catholic, but intertwines really cool Christian themes in his “Silver John” stories: Manly Wade Wellman (real name). By the way: If you’ve read the Silver John stories or novels, *The Long Lost Friend *is a real book; I have a copy.
Walker Percy, Lost in the Cosmos. That haunting option at the end: End of the world, only the progressive, completely secularized group on the one hand, and the Catholic group on the other hand, survive. Which group do you choose to live in?