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.

"Klauck's approach is to select the material most important for the students of early Christianity.... One can say without hesitation that the author has succeeded admirably in his attempt at compressing vast fields of complicated materials into a survey that is both manageable and informative. His key to success was concentration on matters of fundamental important and prudent selection of primary texts, coupled with interpretations and bibliographies reflecting the current state of research.... Klauck's work represents a major achievement."
– Hans Dieter Betz, Journal of Biblical Literature

"[Klauck's volume] offers a well-informed, comprehensive, and valuable guide to the topic, which draws from up-to-date scholarship. The English edition represents not only a very readable translation, but also a revision and updating."
– Juan Garcés, Journal of Theology for Southern Africa