Summary from Goodreads:

Poet, Magician, Mountaineer, Polemicist & Pornographer, Aleister Crowley was the most famous, or infamous, name in 20th century occultism. The popular image of him as, in the words of Francis King, "an insatiable sexual athlete, a pimp who lived on the immoral earnings of his girl-friends, & a junkie who daily took enough heroin to kill a roomful of people", has a basis in fact; but there were other, less obnoxious & despicable aspects of this highly original character. Crowley's greatest legacy is his eclectic occult system. His Magick persists, a potent synthesis of Golden Dawn magic, oriental esoteric techniques, sexual magic & the all-encompassing Law of Thelema with its two fundamental principles, "Every man & woman is a star" & the notorious "Do What Thou Wilt Shall Be the Whole of the Law". With his usual flair, Colin Wilson brings this complex enigmatic figure to life & provides an engrossing portrait of the self-styled Great Beast, the man whom the contemporary press dubbed The Wickedest Man in the World.