George Powers Cockcroft, widely known by the pen name Luke Rhinehart, was an American novelist, screenwriter, and nonfiction writer. He is best known for his 1971 novel The Dice Man, the story of a psychiatrist who experiments with making life decisions based on the roll of a dice.

The Book of est is a fictional account of the training created by Werner Erhard, (est), or Erhard Seminars Training, first published in 1976 by Holt, Rinehart and Winston. The book was written by est graduate Luke Rhinehart. Rhinehart is the pen name of writer George Cockcroft. The book was endorsed by Erhard, and includes a foreword by him. Its contents attempts to replicate the experience of the est training, with the reader being put in the place of a participant in the course. The end of the book includes a comparison by the author between Erhard's methodologies to Zen, The Teachings of Don Juan by Carlos Castaneda, and to Rhinehart's own views from The Dice Man.