Patterson’s Taking With The Left Hand
Taking With the Left Hand: Enneagram Craze, People of the Bookmark, & The Mouravieff “Phenomenon” (Paperback)
The previous link to the enneagram, upon inspection, is filled with the hopeless muddle that came into being with the ‘character types’ enneagram racket.
The book by Patterson gives a good account of the whole history, but preposterously ends by defending the ‘real’ enneagram subject matter of Gurdjieff. The book is nonetheless useful for background information.