In this book Underhill outlines her own view of the mystic's journey into five parts: "Awakening of Self," "Purgation of Self," "Illumination," "the Dark Night of the Soul," and "the Unitative life." Underhill is focussed on mysticism in Christianity but she also mentions Sufism, Hinduism, Buddhism. This semnial work has long been considered a crucial treatise on the subject of Mysticism, and continues to be so even today.