He: Understanding Masculine Psychology
By Robert A. Johnson
He is the companion piece to She, We, and other helpful works in a series of psychological primers Johnson has published. It is an excellent and helpful introductory book for understanding the masculine psyche through mythology, archetypes, and Jungian psychology.
If one were to read it alongside his other brief works, which are all around 100 pages, one would have a wonderful foundation from which to build further.