Reminds me of a sci-fi classic not talked about much anymore, A Canticle For Leibowitz by, um, Walter Miller I think, from the late 50's.
An old Jewish guy, Mr. Leibowitz (Diablo 3 Gold), is on his way to the store for his wife when a nuclear war destroys all civilization as we know it. He survives and becomes part of an underground order of monks dedicated to saving human technological knowledge (which has been banned as evil by the post-war world government). 3000 years later, the order is going strong and he's been regarded as a saint all that time. But the book actually opens when someone finds a new artifact fragment attributed to St. Leibowitz. A sub-order of monks devotes itself to studying it, over lifetimes. Interpretations of it cause major schisms. But as we read it, we know it to be the grocery list Mrs. Leibowitz gave her husband.
The book is actually deeply philosophical and is considered a work of literature (Diablo 3 Gold), not shoot 'em up sic-fi. I read it when young, maybe 13, and I know I skipped over pages because it was a difficult read. This reminds me that I've wanted to re-read it.