This fascinating book discusses the role played by psychoactive mushrooms in the religious rituals of ancient Greece, Eurasia, and Mesoamerica. R. Gordon Wasson, an internationally known ethnomycologist who was one of the first to investigate how these mushrooms were venerated and used by different native peoples, here joins with three other scholars to discuss his discoveries about these fungi, which he has called entheogens, or "god generated within".

In the book Wasson describes his quest for the soma plant, which led him to the Middle East and India, to shamanic rites of Siberia, Mesoamerica, and the United States, and to the folklore of Europeans, Bedouins, and even the Pennsylvania Dutch. Stella Kramrisch details the rituals of the putka mushroom, a later substitute for soma. Jonathan Ott comments on the "disembodied eyes" found on carvings in Mexico and on an ancient ring from Crete, eyes that he argues are metaphors for the state produced by ingestion of entheogenic mushrooms. Finally Carl A.P. Ruck relates a variety of fungi to Greek myth and ritual, focusing in particular on ergot, a common growth on barley that he feels may have been imbibed at the Eleusinian Mysteries.

The late R. Gordon Wasson, a pioneer in the field of ethnobotany, was the author or coauthor of numerous books including Soma, Divine Mushroom of Immortality.