"A Professional Occultist on Improving the Realism of Magic Systems Used in Fantasy Simulation Games"
The original version was first published in 1978. A revised reprint was published by Chaosium in 1979.
From the back cover of the revised printing:
"At last! A book on the basic theory and practice of real world and religion. Specifically written for the tens of thousands of players who are devoted to fantasy simulation games. One of the greatest living authorities on parapsychology, the occult and other minority belief systems offers readers the benefit of his years of professional training as a ceremonial magician, psychic and teacher. Whether you "believe" in psychic powers or not, the author of the classic occult text, "Real Magic," will convince you that it IS possible to get game magic systems that will accurately reflect the theories and practices that magicians and clerics in the real world have been using for centuries, without having to sacrifice playability for realism.
"Based on a detailed analysis of every currently popular fantasy simulation game, "Authentic Thaumaturgy," is bound to find a place in the reference library of every fantasy game player."