What does Faber say books are for?

From the text:

The books are to remind us what asses and fools we are. They're Caesar's praetorian guard, whispering as the parade roars down the avenue, `Remember, Caesar, thou art mortal.' Most of us can't rush around, talking to everyone, know all the cities of the world, we haven't time, money or that many friends. The things you're looking for, Montag, are in the world, but the only way the average chap will ever see ninety-nine per cent of them is in a book. Don't ask for guarantees. And don't look to be saved in any one thing, person, machine, or library. Do your own bit of saving, and if you drown, at least die knowing you were headed for shore."