Liber Aleph -- the Book of Wisdom or Folly -- is one of Aleister Crowley`s masterworks, written in New York City at the end of the First World War. He described it as `an extended and elaborate commentary on The Book of the Law, in the form of a letter from the Master Therion to his magical son.` It is an educational treatise in the purest sense, that of the transmission of hard-won wisdom from generation to generation. Crowley sets out an impressive array of spiritual concepts in two hundred and eight chapters, and turns from one subject to the next` with a wondrous continuity as he pours out his encyclopedic knowledge. The Holy Qabalah, magick, the psychology of dreams and the unconscious, the formula of initiation, the education of children and the training of disciples, the mystical trances, drugs, sex, love and death; these are but a few of the topics treated, not in passing, but in profound depth. The book is deliberately couched in an archaic, epistolatory style that is strangely suited to its many difficult subjects. In his later life Crowley would turn to Liber Aleph again and again, quoting entire chapters to elucidate a principle, or referring readers to the book for a full treatment of a particular topic. It is possibly his most comprehensive exposition of his mature magical philosophy. This revised second edition was edited by Hymenaeus Beta, Frater Superior of the O.T.O., and includes an historical study of the circumstances, personalities and issues connected with the work`s creation.