Klauck's is a uniquely well-informed and comprehensive guide to the world of religion in the Graeco-Roman environment of early Christianity. Drawing on the most up-to-date scholarship, his volume paints a carefully nuanced portrait of the Christians' religious context. Besides describing ordinary domestic and civic religion and popular belief (including astrology, divination and "magic"), there is extended discussion of mystery cults, ruler and emperor cults, the religious dimensions of philosophy, and Gnosticism. An authoritative work, Klauck's will become a new standard for reference and teaching.