There is an interesting and thought provoking essay on the pleasures and possible benefits of re-reading over on BBC Culture. The assuredly non-scientific (no complete citations or statistics) essay has some food for thought, especially in how the book being re-read gains context depending on the complete experiences of a person, including books read in the meantime.
But even without the aid of marginalia, these texts can carry us back to a time and place, and remind us of the kind of person that we were then.
We’re changed not only by lived experience but also by read experience – by the books that we’ve discovered since last reading the one in our hand.