seeing through

One of the problems of being a writer is when you read, you see why the author wrote something. You are shore that the writer pondered how to get the information across, the same way you are when you try three or four different methods.
I was reading a novel this morning where the main character is doing a bio of his great grandfather. He has copies of the letters the man received, but how does he know what his grandfather wrote?
Simple the author, explains the grandfather wrote a copy of the letter he sent.