You are what you read. If you don’t read, like if you don’t eat, you may not be a lot.
Of course, as Richard Foster points out in The Celebration of Discipline, there are all sorts of books we can read and learn from. I do not merely mean types or genera’s of literature, I mean there are other things that we can “read” and learn from. Such as the universe and other people. I do not mean, of course, that if you read Crime and Punishment then you’ll be a murderer or if you read Dracula that you’ll be a Vampire. I mean, rather, that what you read, and how you read, will affect your person.
Further, like eating, there is a time for ice cream—and we should enjoy it!—but we must not forget that our diet should not consist of ice cream. We must eat meat and even lima beans from time to time.
As part of our book diet, C.S. Lewis reminds us to not leave out old books. “It is a good rule, after reading a new book, never to allow yourself another new one till you have read an old one in between. If that is too much for you, you should at least read one old one to every three new ones” (C. S. Lewis, “On the Reading of Old Books”).
Lewis is wise to also say that,
“People were no clever then than they are now; they made as many mistakes as we. But not the same mistakes. They will not flatter us in the errors we are already committing; and their own errors, being now open and palpable, will not endanger us. Two heads are better than one, not because either is infallible, but because they are unlikely to go wrong in the same direction” (C. S. Lewis, “On the Reading of Old Books”).