Small but significant. A Canticle for Leibowitz by Walter Miller comes immediately to mind. (And readers of this thread who did appreciate the religious themes of Hyperion may be interested.)

I adore Canticle. It is one of my favorite books.

I had recommended Hyperion to a friend, and they loved it. I recommended Canticle as a follow-up and they hated it. I never figured out how that can be.