Bremmer, Jan N., Initiation into the Mysteries of the Ancient World (De Gruyter, 2013), has been published now as an ‘Open Access’ book, thus downloadable to read (thanks to Larry Hurtado for the info).
The publisher states: “It gives a ‘thick description’ of the major Mysteries, not only of the famous Eleusinian Mysteries, but also those located at the interface of Greece and Anatolia: the Mysteries of Samothrace, Imbros and Lemnos as well as those of the Corybants. It then proceeds to look at the Orphic-Bacchic Mysteries, which have become increasingly better understood due to the many discoveries of new texts in the recent times. Having looked at classical Greece we move on to the Roman Empire, where we study not only the lesser Mysteries, which we know especially from Pausanias, but also the new ones of Isis and Mithras. We conclude our book with a discussion of the possible influence of the Mysteries on emerging Christianity.”
The book kan be downloaded in chapters (as pdf files), or as a whole.