Claudio Naranjo was a Chilean psychiatrist. He was co-developer of the Enneagram of Personality. His studies and investigations oftenly focused in the search of spirituality to find mental stability, and also some times, the use of lisergic substance to free hidden and harmful thoughts.
Original research material from Naranjo, so invaluable info for understanding the Enneagram. Not a book for everyone, though. Best for actual psychologists or advanced Enneagram practitioners. Otherwise it will be very hard to read.