No book is really worth reading at the age of ten which is not equally – and often far more – worth reading at the age of fifty and beyond.
There's nothing wrong with reading a book you love over and over. When you do, the words get inside you, become a part of you, in a way that words in a book you've read only once can't.
There are too many books in the world to read in a single lifetime; you have to draw the line somewhere.
