Annie is referring to the worlds that can be opened to us through books and reading. She is a lover of books and learning and this statement reveals that love. With books and writing, we can read as far back into history as the first time a person took an instrument and attempted to record his thoughts - maybe on a cave. She uses a metaphor, "the light of words." This means that words shed light on history. Also, when we are reading words, we ourselves become "enlightened" by what we are reading. The written word allows us to learn about what has come before us - even as far back as five thousand years.