If a book is good, re-reading it is not at all the same experience every time. You greet some passages like old friends, others that you may not have noticed before may surprise you. There are both reunions and discoveries, hidden gems along with the comfortable friends. A familiar book is no more a rut than having dinner with the same friend twice, or dancing to the same music twice. Even if they are the same, you are always different from one read to the next, and thus, so is the experience.