"The Book of the Law" is a central text in the philosophy of Thelema, written by Aleister Crowley in 1904. It is considered a sacred scripture by followers of Thelema and outlines the principles of individual will and personal freedom. The text emphasizes the idea that each person has a unique purpose and should pursue their true will. The book is divided into three chapters, each attributed to different deities, including Hadit and Nuit. It introduces the famous phrase "Do what thou wilt shall be the whole of the Law," which encapsulates its core message of self-discovery and empowerment.