Below are the best books we could find on Enneagram.
The Enneagram is a system for identifying nine personality types through our behavior patterns, each with its own gifts and strengths, as well as challenging or shadow traits. They are represented by the points of a geometric figure called an Enneagram, which indicates connections between the types. Though its origins are the subject of some dispute, the Enneagram as we know it today was conceived of by Bolivian philosopher Óscar Ichazo; his ideas were developed further by Chilean psychiatrist Claudio Naranjo in the 1970s. Naranjo was also influenced by some earlier teachings about personality by the Russian philosopher and mystic and George Gurdjieff.