Every book worth reading at all should immediately be read twice, partly because we understand things better in their context the second time and only really understand the beginning when we know the end, and partly because we bring a different spirit and mood to every passage the second time around, which makes for a different impression and is as if we view an object in another light. (Schopenhauer, Parerga and Paralipomena)

How is “real book” defined? Quite simply: it is a book one wants to reread. It can stand rereading because it is very full – of ideas and feelings, of scenes and persons real or imagined, of strange accidents and situations and judgments of behavior: it is a world in itself, like and unlike the world already in our head. For this reason, this fullness, it may well be “hard to get into.” But it somehow compels one to keep turning the page, and at the end the wish to reread is clear and strong: one senses that the work contains more than met the eye the first time around. (Jacques Barzun, Begin Here: The Forgotten Conditions of Teaching and Learning)