I've been thinking about what makes a book worth rereading as opposed to worth having read. Most books fall in the second category — they did what they did once and do it again less well when you already know the outcome. A smaller number genuinely improve on rereading.

The books that improve on rereading are typically the ones where the method is as interesting as the outcome. Gilead improves on rereading because once you know Ames is dying, the texture of his attention to ordinary things becomes unbearably poignant. Never Let Me Go improves because the novel is saturated with information that the characters are not able to fully process, and on rereading you see it everywhere.

The common factor seems to be novels with a significant gap between what is said and what is shown. The first reading fills in the gap with uncertainty. The second reading fills it in with knowledge. The second filling is the richer experience.