To the world, he was Dr. Sacks, the brilliant neurologist behind bestselling books like Musicophilia and The Man Who Mistook His Wife for a Hat. To professor Susan Barry, he became Dear Oliver--her mentor, friend, and confidant over the course of their unlikely, engrossing ten-year correspondence. It begins with a letter that Sue almost doesn't send. Dear Dr. Sacks . . . You asked me if I could imagine what the world would look like when...