The Wisdom of the Enneagram by Don Richard Riso & Russ Hudson

The sub-title reads The Complete Guide to Psychological and Spiritual Growth for the Nine Personality Types. The personality type of the Enneagram include (1) the Reformer (2) the Helper (3) the Achiever (4) the Individualist (5) the Investigator (6) the Loyalist (7) the Enthusiast (8) the Challenger (9) the Peacemaker.

The book includes two questionnaires to determine your personality type. A full explanation of all nine personality types, including insight into the motivations, fears and desires of each personality type and also their potential and pitfalls.