Once out of school, most of us read for pleasure. Yet there is another equally important, though often overlooked, reason that we read: to learn how to live. Though books have always been understood as life-teachers, the exact way in which they instruct, cajole, and convince remains a subject of some mystery. Drawing on sources as diverse as Dr. Seuss and Simone Weil, P. G. Wodehouse and Isaiah Berlin, Pulitzer prize-winning critic Michael Dirda shows...