I've been looking for this PDF to share for a very long time. This is the description given :
A compendium of the teachings and rituals of a Pagan religious order - the Ordo Arcanorum Gradalis - based upon the Holy Grail legends. The book covers the teachings and concepts of the order, and contains a compilation of its sacramental rites and seasonal rituals.
I would like to add that it is the only workable union of Gnostic Christianity, Grail Mysticism, and Pagan God/Goddess religion that I have ever found. This volume is dense, fascinating, practical, and IMHO absolutely essential.