A Canticle For Leibowitz- by Walter M. Miller, Jr.
sci-fi story written in the mid-1950's, about a new (post-atomic) Dark Age,
where generations of angry hordes have put down every scientist and intellectual (angry about the horror and destruction they caused with the Bomb),
and "simpletons" and illiterate hunter-gatherers populate the continents,
with the exception of a few monasteries that's been allowed to hold onto religious tradition and the study of Scriptures and illuminated manuscripts...
a long time ago, at the time of the post-atomic Deluge, a man called Leibowitz (a scientist) was accepted into the Brotherhood of monks, and swiftly became one of the most popular among them- he made the Order into one whose chief goal was to travel around and gather the few remaining books that hadn't been destroyed in the mob's great Simplification, and these should be saved and copied by the monks for generation after generation,
to preserve the last bit of knowledge...
amusingly, it seems like many of these "manuscripts" were actally technical manuals and circuit diagrams...
(which the monks didn't understand, but faithfully reproduced illuminated manuscripts of)
i haven't read the rest yet, but i think i can see where this is heading...