Michael B. Cosmopoulos 
Greek Mysteries [PDF ebook] 
The Archaeology of Ancient Greek Secret Cults

Written by an international team of acknowledged experts, this excellent book studies a wide range of contributions and showcases new research on the archaeology, ritual and history of Greek mystery cults. With a lack of written evidence that exists for the mysteries, archaeology has proved central to explaining their significance and this volume is key to understanding a phenomenon central to Greek religion and society.