In 1578, during months of imprisonment for his reformist beliefs, San Juan de la Cruz composed a series of narrative poems inspired by the Biblical Song of Songs--and, the story goes, a popular love song overheard from his cramped cell--that take God as the beloved. Erotically charged, initially scandalous, his mystical poetry engages with the journey of the soul through the darkest trenches of suffering and despair toward an enlightened...