Magick in Theory and Practice by Crowley, Aleister (1992)

Understand Ritual and Ceremonial Magick in the Modern Era
"MAGICK is the Science and Art of causing Change to occur in conformity with Will."
-Aleister Crowley, from the Introduction
Magick in Theory and Practice is Part 3 of Aleister Crowley's four-part masterwork Magick: Liber ABA, Book Four, a foundational resource of modern magick, occultism, and hermeticism. Crowley's unparalleled knowledge of magick (which is defined as the effort, in Wicca and certain other belief systems, undertaken to affect personal transformation or external change), acquired as both scholar and practitioner, made him one of the world's leading experts on the subject. He was a British occult mystic who even created his own esoteric, magick-based spiritual philosophy called Thelema, for which he wrote the sacred texts.
In Crowley's broad view, magick represents the act of affecting the world through thoughts and actions. Often known for his sensational teachings and self-created diabolical image (he was infamously known, in his own words, as "the Wickedest Man in the World!"), Crowley here provides an accessible and comprehensive entry into the world of magick for all readers. Synthesizing the most salient elements of his many other writings on the subject, this insightful and instructive volume focuses specifically on how to understand and perform ceremonial magick. Part 1 thoroughly explores definition, theory, formulas, methods, and philosophy of magick, along with the importance of self-discipline. In the second half, Crowley illuminates and provides instructions for several of the most significant magical rituals, including the Star Ruby banishing.
Replete with useful advice, copious footnotes, and a comprehensive bibliography, Magick in Theory and Practice includes helpful instructions for creating conducive mindsets and appropriate physical settings for practicing magick. It is a must-read for any aspiring magus, mage, practitioner of magic, or student of the occult, and a belongs in every magician's library.
This book is also available from Echo Point Books as a paperback (ISBN 1648370101).