You will read in a book that (correct?)
I was reading a story called "The Journey to Hanford" in a book titled "Great American Stories 1".
In that story, I found the expression "You will read in a book that..." about three times. But to me, a non-native English speaker (an English learner), I find confusing the use of that expression and was wondering if its use is correct.
Here is the context:
"I won't have him singing all day," my grandfather roared. "Some things simply have to stop, in the end. You will read in a book that a father loves a foolish son more than his wise sons. Believe me, that writer is not married, and also he has no sons."
"Away with him and his zither both," my grandfather said. "You will read in a book that a man can sit all day under a tree and play music on a zither and sing. Believe me, that writer is a fool. Money, that's the thing. Let him go and The Journey to Hanford work under the sun for a while. In the watermelons. Him and his zither both."
"Foolish words!" my grandfather said. "You will read in a book that a man who sings is truly a happy man. But that writer is a dreamer, not a businessman in a thousand years. Let him go. It is twenty-seven miles to Hanford. That is a very good distance."
If so, is it really expressing future? What kind of future? Because I would expect something like "You may/might read in a book that" instead. So I would expect something expressing possibility.