"What we don't know about ourselves can and will hurt us, not to mention others. As long as we stay in the dark about how we see the world and the wounds and beliefs that have shaped who we are, we're prisoners of our history. We'll continue going through life on autopilot doing things that hurt and confuse ourselves and everyone around us. Eventually we become so accustomed to making the same mistakes over and over in our lives that they lull us to sleep. We need to wake up." --Brother Dave as quoted in The Road Back to YouThe Enneagram says that there are nine distinct personality types and ways of how people see the world. In order to protect ourselves from feeling vulnerable, we adapt ways of thinking, doing, and feeling. These adaptations are on a continuum of healthy and unhealthy.
The Road Back to You explains each Enneagram type and what it's like for each type to be in the world, in relationships, and at work. There is also a section describing what transformation for each type would look like.
An effective book because of its clear writing and also the personal stories included. If you're looking for a way to understand yourself better and those around you, this is a great introduction to the Enneagram.