From publisher blurb:
Echelon Reference Series: Monks collects information about the monk class. The monk base class, the unchained monk base class, and 27 monk archetypes – monks have many class features to trade out, and can support a wide variety of options. Monks (mostly) don’t have class features to choose from such as rage powers, but they do get bonus style feats every fourth level… this book has 20 martial arts styles, and 140 other feats. There are also over 30 stat blocks for NPCs of all levels and many races.
This is the 3pp+PRD version, containing information from the PRD and selected third-party products.