Aleister Crowley has an extensive and notorious reputation making him nearly a household name, if not per virtue of his deification by Ozzy Ozborne, The Beatles, Iron Maiden, and numerous other Trumpeters of the Apocalypse, then by his moniker "666". His attacks against Law, Religion, and Moralisms have made him a firgue variously revered, feared, and despised. Crowley's influence on popular culture was as tangible in his time as now, but this is only his effect on the larger public. His esoteric relevance to the modern world is continued through the Ordo Templi Orientis.

Crowley (aka Phoenix as the OHO of OTO and Baphomet as X* of the British Isles) was initiated into OTO in 1910 and within two years became crowned the Supreme and Holy King (X*) of the British Isles. He reformulated the initiations of the OTO in the spirit of Thelema, The Book of the Law, and Magick. He reconciled the disparities of numerous branches of Freemasonry and bound them to the principles of Thelema and Agape, transforming the initiations, practices, and procedures of OTO accordingly. 
Aleister Crowley was a prolific writer and a full collection of his works would both bless and burden any bookcase. Much of his literature is in direct reference to the Initiations of OTO, and vice versa. Any person considering Initiated membership in OTO is strongly recommended to begin exploring the writings of Aleister Crowley. Any Thelemite (adherent of Thelema) who values the attainment of honor through renunciation, and the possibilities of cooperative endeavor can look forward to the OTO as a promise of Thelemic Community and Magical Insight.

For more information on Aleister Crowley,  Do What Thou Wilt by Lawrence Suttin, Perdurabo and The Weiser Concise Guide to Aleister Crowley by Richard Kaczyinski, are good resources.