Wicca is one of the few traditions in this atlas whose emergence is documented in living memory, in print, and in the papers of the people involved, and that visibility has been uncomfortable for some of its claims about itself.
The tradition became public through Gerald Gardner, who published Witchcraft Today in 1954, shortly after the repeal of the British legislation under which such claims could have been prosecuted, and The Meaning of Witchcraft in 1959. He presented what he described as a surviving pre-Christian religion into which he had been initiated.
Subsequent research has examined that account closely. Historians have traced identifiable components to sources available to Gardner: the ritual magic of earlier societies, ceremonial and literary material, folklore scholarship of the period, and an academic thesis about a witch cult surviving from antiquity that was influential when he wrote and is no longer accepted. What the evidence supports is a religion assembled in the mid twentieth century from older materials rather than transmitted intact from before Christianity.
Most practitioners today are comfortable with that, and the tradition's own historians have done much of the work establishing it.
The Book of Shadows, the working text, is copied by initiates and varies between lines. Versions have been published, which the initiatory lines regard differently, and the tradition has diversified far beyond its original form.