How is reading a piece of literature a conversation with the author? (even if the author has been dead for a thousand years)

From the text:

We have to bring our imaginations to bear on a story if we are to see all its possibilities; otherwise it’s just about somebody who did something. Whatever we take away from stories in the way of significance, symbolism, theme, meaning, pretty much anything except character and plot, we discover because our imagination engages with that of the author. Pretty amazing when you consider that the author may have been dead for a thousand years, yet we can still have this kind of exchange, this dialogue, with her. At the same time, this doesn’t indicate the story can mean anything we want it to, since that would be a case of our imagination not bothering with that of the author and just inventing whatever it wants to see in the text.