Anathem by Neal Stephenson has some of that vibe. If you haven't read it, I'd recommend reading it without even glancing at the Wikipedia page or plot synopses to avoid conceptual spoilers.

It doesn't have tone in common with post-apocalyptic fiction. I'd call it "alternative future", not that it's easy to pigeonhole!

It absolutely is germane to this conversation and thanks for reminding me of it.

I think HN would enjoy it very much. It's an astonishing novel. Read it!

"A mote in god's eye", by Niven & Pournelle covers a very similar setup, although not on earth. It's also quite good.