I wish I had known that I wasn't going to see Mr. Black again when we shook hands that afternoon. I wouldn't have let go (Chapter...

"I wish I had known that I wasn't going to see Mr. Black again when we shook hands that afternoon. I wouldn't have let go" (Chapter Fifteen, A Simple Solution to an Impossible Problem). How far would you agree with the statement that Extremely Loud & Incredibly Close is about "letting go"?