Sometimes unread books on a shelf are as good as a diary entry to jog the memory. You look at the spine of a novel you bought twenty years ago at the Strand bookstore in New York. Remember you were with so and so that day. You hadn’t seen them for a long time. They didn’t want to go to the store but did you a favor when you said you only needed a few minutes to see if that book was there. You’d read very positive reviews. Later you had good pastrami sandwiches for lunch and talked about…

You’ve n...