Charles Williams' book is devoted to the study of the relationship between magic and the Church and is based on a large amount of factual material. The author, an Anglican by faith, a mystic by conviction, one of the most unusual theologians of the twentieth century, believed that spiritual exchange between worlds occurs continuously, although the influence of the invisible world occurs almost imperceptibly. As one of the "Inklings", Williams did a lot for the mythopoetic revival in modern culture.