The Book of the Law, the holy text that forms the basis of Thelema, was transmitted to Crowley by the entity known as Aiwass in Cairo, on three successive days during April 1904. Acting as a medium, Crowley recorded the communications on hotel notepads and later organized his automatic writing into a short, coherent document. Aiwass/Crowley presents The Book of the Law as an expression of three god-forms in three chapters: Nuit, Hadit, and Ra-Hoor-Khuit.

Practical Mysticism is an outstanding guide to experiencing and understanding mystical experiences by renowned scholar Evelyn Underhill. Underhill's books are appreciated and praised to this day by scholars and enthusiasts of spiritualism, and even psychologists seeking explanation of the spiritual component of human behaviour. In Practical Mysticism, the author introduces and unveils key tenets of mysticism for the ordinary reader. Highly inclusive, Underhill proposes that the spiritual discoveries and self-discovery of mysticism are available to every person, and that all it takes is the will and persistence to embark on the voyage. Although praised for her work on Christian mysticism, Underhill is careful to note that her general take on spiritual experiences is not tied to one, or indeed any, formal religion. Rather she is of the opinion that the journey to spiritual awakening is a vital one for those wishing to better understand and come to terms with the complex universe we live in.