Secret Agent 666 is a terrific read. Author Spence is no kind of expert on occultism, and seems basically unperceptive on even such related topics as Freemasonry. But he does have useful expertise on British espionage in the first half of the 20th century. Although Spence has documentary support for Aleister Crowley's status as an asset of the British intelligence apparatus, he also uncovers evidence of apparent "scrubbing" throughout the archives of various UK and US agencies. Much of the narrative he presents, then, is admittedly speculative.

The best-supported details for Crowley's career as a propagandist agent provacateur are those for the World War I period, and perhaps as much as half of the book focuses on that interval. Spence's references are far-ranging, and include sources of dubious value, but the conclusions he draws from them are still credible, and framed with appropriate caveats. His most important source throughout is Crowley's Confessions (and not just the published version), to which he brings vast amounts of missing context by identifying the political allegiances and intelligence activities of Crowley's many associates.

The presentation refrains from any attempts to interpret Crowley's "Secret Chiefs" as his superiors in espionage. In fact, his supervisors were more likely to appear in the form of his A.'.A.'. pupils, such as Gerald Yorke. Still, anyone interested in the intersection between occultism and international politics would be well-served by placing this book on a reading list just next to K. Paul Johnson's works on the Theosophical Masters.

Spence is in no hurry to make Crowley either a villain or a hero. He does opine that the Beast was always a loyal Englishman, who relished clandestine intelligence and propaganda work, and had a long history of doing such work. Also, he disclaims any reductionism with respect to Crowley's occult activities: The fact that a particular magical retirement might have have been opportune for a certain spy operation does not mean it wasn't also a genuine spiritual undertaking. For those already familiar with Crowley's general biography and magical accomplishments, the result is the restoration of missing pieces of the mage's career, with reasonable explanations for many previously-murky travels and initiatives.