The idea of a massive, extremely long "dark age" in the future is one of the premises of Asimov's Foundation series. One of the early protagonists had an intere

The idea of a massive, extremely long "dark age" in the future is one of the premises of Asimov's Foundation series. One of the early protagonists had an interesting approach to solving it, a sort of covert galactic Library of Alexandria. I highly recommend the series if you find this idea interesting, enjoy Asimovian science fiction, or are a living human being.