These people are a group of former intellectuals and librarians who have fled civilization and live in the wilderness. They have committed entire books to memory, carrying the knowledge and wisdom of the past within themselves.
The most prominent example is Granger, the leader of the Book People, who recites lines from Shakespeare's *The Merchant of Venice* and other works.
However, it's important to note that the book doesn't specify exactly which books they memorize. The focus is on the *idea* of preserving knowledge and the resilience of the human spirit, not on the specific titles themselves.