In "A Canticle for Leibowitz", Walter M. Miller, Jr. used a group of monks who focused mostly on storing "Artifacts", ie objects from the past, which they later used as a way to recover some of their lost knowledge since the books all got destroyed by angry mobs during a period called "The Simplifying". The humorous part was that those who did this huge book burning called themselves "Simpletons".
But anyways, he used the monks of a Catholic monastery who went out just shortly before and during the simplification (and at times afterwards when other artifacts were found) which were then later brought out and parsed in order to recover as much lost knowledge as possible.
Ultimately though I think a lot of information would need to be relearned again, the same as what happened after the fall of the Roman Empire. Sure, you can save some knowledge via books and the like. But there's so much other information that can't be written down or recorded for posterity as it's things you can only learn by experience, on the job, or through apprenticeship. It's that "soft knowledge" that would be the first to go and the hardest to perpetuate initially until the number of available minds returned to the levels required to properly perpetuate it.