It is not really possible to re-read a book, just as it is not really possible to step into the same river twice. The next time, one's thinking is going to be entirely different. I have read "LoTR" half a dozen times. Each has been different. I think Heraclitus even said you couldn't step into the same river even once. I know what he's talking about. Every single time is a new time.
I remember when I was seven being bored stiff reading and rereading the reading scheme books for my 'assessed reading age' at school. The problem was that I was being assessed by my ability at reading aloud and not allowed to progress until I had read each one to the teacher. I was already a silent reader of proper books from the Praça de Chile Library and could read the scheme books a dozen times before I was called.
If you're into stuff like this, you can read the full review.