This is a masterfully told story, with well developed characters, and it makes brilliant dramatic use of the scanty available evidence on the prehistoric Germanic tribes. It does not deserve the commentary in the review below. It does appear that religion among the early Germanic tribes was a more personal affair. But it is wrong to say that the seeresses were not professional ("Berufs") practitioners.
To quote H.R. Ellis Davidson, an English scholar and leading expert on the Germanic and Celtic culture of the Roman Iron Age: (from Myth and Symbol in Pagan Europe): "While there is little evidence in Germany for the existence of a closely-knit priestly class...this does not mean their practices were fundamentally different from those among the Druids in Gaul. There may have been more individualism among the Germans, but most of our information comes from a late period, and an organised priesthood could hardly have survived in strength in Iceland. And in Germany there is evidence for one important class of women, the Seeresses, who took on the duty of interpreting omens and making enquiries on behalf of the people. They seem to have possessed considerable politcal influence, which can be compared with that of the Druids."
One such professional seeress was the Veleda of the Bructeri, whose very name was a professional title, meaning "seer". Surviving Icelandic texts that discuss the Veleda's "descendants" in early medieval Iceland show us professional seeresses who were organised into colleges of nine, and had vital tasks in the community, such as traveling from farm to farm, giving oracles. Icelandic literature makes it clear that the seeresses were keepers of the knowledge of the tribe's remote past--just as Julius Caesar claims the Druids were. Reason suggests this requires professional training.
Davidson goes on to state that the Veleda was likely part of a religious community. And the study of shamanism strengthens this claim. The anthropologist Barbara Tedlock, Ph.D., stresses in her works that Germanic seeresses were part of a greater shamanic tradition. There are parallels, worldwide, for the multiple societal tasks shamans perform, which include vision quests, mediumship, knowledge of the plants, and shapeshifting. Such practitioners would of necessity have had to have a long preparation for their role, such as the Druids had; in this case, absense of evidence is not evidence of absense. In every culture, shamanism is a professional role.
And so I would say that the way the author of Mondfeuer uses this material, and how adroitly she fills in gaps, is in accordance with the small but critical evidence we possess, and that the review below is patently unfair. This book powerfully evokes the atmosphere of the times, which is what we should expect from good fiction.