Answer:
We limit ourselves
Explanation:
With books it´s the same as with people: the more diverse the books you read or the people you meet, the more your mind opens up to different views of how the world is or could/should be. Totalitarian regimes - as the one presented to us in Fahrenheit 451 - can be succesful exactly in situations where everybody follows blindly one personal view (that of the leader) or, as in religious fundamentalism, one book.
