Maasai religious knowledge is transmitted orally, within age sets, families and the lineages that hold ritual office, and it was not written by those who held it.
The outside record begins with nineteenth-century European travellers and missionaries in East Africa and expands under British colonial administration, which had a practical interest in Maasai social organisation because it was governing and displacing Maasai communities. The age-set system, the office of the oloiboni and the prophecies attached to it are documented from that period, in accounts written by people whose administrations were reducing Maasai land.
The Maasai also became, and remain, one of the most photographed and most commercially represented peoples in Africa. That has produced an enormous popular literature which is about an image rather than about a religion, and a reader looking for the tradition has to get past it.
Twentieth-century anthropology produced serious work on Maasai social and ritual organisation, and from the later part of the century Maasai scholars and community organisations have written about their own tradition and about the land and rights questions inseparable from it.
The religion is living and is practised alongside Christianity by many Maasai today, in combinations that vary by family and by community. The atlas describes the structure of the tradition and leaves what is held within lineages and offices with them.