From Italo Calvino's The Uses of Literature---

1. The classics are the books of which we usually hear people say, "I am rereading . . . " and never "I am reading . . . "
2. We use the words "classics" for books that are treasured by those who have read and loved them; but they are treasured no less by those who have the luck to read them for the first time in the best conditions to enjoy them…