 By the end of the Maya Classic Period it is assumed that Maya libraries housed thousands of books, written on bark paper or deer skin.These libraries contained codices that covered important subjects such as genealogy, astronomy, rituals, information about plants and animals, medical knowledge, and history.It was said that the Aztec city of Tenochtitlan, had become such “a splendid city that, according to records, it dazzled the Spaniards.” The Aztecs had an advanced prosperous civilization.