Ronin adds new options for both players and referees to add an action slant to a game. The new role of Ronin is the thematic anchor of this supplement.
A ronin is generally less supernatural than a typical PC but just as dangerous. Included are details of the Ronin faction, NPCs a Ronin might encounter and a few new traits that I would describe as pretty powerful.
The 2nd half of this supplement comes in the form of "Downtime" rules which players can use to pursue personal or group goals between missions. These mechanics are mostly fueled by the players giving opportunities to experience plot points and storyline that might not come naturally to a mission. It's a great tool for players that want to add depth and dimension to their personal storytelling.
Whether, you want to explore the world of Ronin or are looking to add some of your own story between missions "Ronin" is recommended!