The book consists of 80 letters to various students of magick. Originally to be titled Aleister Explains Everything, the letters offer his insights into both magick and Thelema—-Crowley's religious and ethical system—-with a clarity and wit often absent in his earlier writings. The individual topics are widely varied, addressing the orders O.T.O. and AA, Qabalah, Thelemic morality, Yoga, astrology, various magical techniques, religion, death, spiritual visions, the Holy Guardian Angel, and other issues such as marriage, property, certainty, and meanness. The book is considered by many as perhaps Crowley's most notable contribution to the occult studies, defining magick for the 20th century.