I have to respectfully say that I disagree with the premise of your entire post. To suggest that what we consume today with our eyes (or ears for that matter) has no effect on our future selves is false. If this were true, advertising (just as one easy example) would have zero effect on the choices people make. I believe what we see, read, and hear has a profound effect on what we think, what we say, and what we believe. You say you don’t believe the Bible nor the Koran are non-fiction. That’s cool. Maybe I don’t either. But is it possible that somewhere along the line something you were told or something you read (or the aggregate of multiple things over and over) made you decide to only believe in that which is provable? (Not trying to speak for you and imply that’s what you believe, just wondering out loud.)
To say that we are impenetrable fortresses against all that is shown to our eyes (or ears) is not something I agree with. Whether it be the written word in books, the spoken word in speeches, movies and songs or the images we see in visual art. All of these things are woven together to make the fabric of our society. Our culture. And the culture we live in has a profound effect on who we are and who we are going to become.
Now sure, maybe some people have thicker skin than others. Maybe you’re one of them. Maybe you are swayed less by what you read today. But wouldn’t that ability to steadfastly stick to your current beliefs be nothing more than a testament to everything you were taught (via the written and spoken word) up until this point?
To say that books, whether fiction or non-fiction, have no effect on people is, I believe, turning a blind eye to history. Provable, verified, history that has been documented…..in books.