Sci-fi and Heroic Fantasy discussion

I’ve always loved when sci-fi blends with mysticism — what’s a book that really nailed that balance for you?

My brain went "Dune" and kind of stopped there so I'm curious to see what else people suggest

It's not mysticism the way that Dune is, but Peter Hamilton's Night's Dawn trilogy does feature the dead returning, although a scientific explanation is provided.

The excellent Canticle for Leibowitz is post-apocalyptic with a heavy dose of mysticism. Both Gene Wolfe's Book of the New Sun series and Jack Vance's Dying Earth series fit into that genre - it was a lot more common in the 60s and 70s to write books in the science fantasy genre.

And, of course, the 40K universe has the Imperium which worships the eternal God-Emperor.