The giant rabbit hole in our lives, the dark kingdom we all visit regularly, is sleep. Sleep is a perfect mystery for most of us. We need it, we want more of it, and we long for it to be of a deeper, richer quality. On one hand, we know it can betray us on any given night. On the other, we know that there’s some alchemy going on during those unconscious, dream-filled hours, some mixing of fact, fantasy, and feeling that can turn our daytime struggles to master new skills into that most precious thing—understanding.