From the back of the book:
Age of Anarchy is a role-playing game set in Norman England at a time of civil strife which lasts for two decades. It's a game grounded in real history, but not constrained by it. It's a time of knights and castles, war and politics, commoners and priests.
In the game, you play the most trusted vassals of a low-ranking noble who seeks to rise up through the ranks of feudal society. You benefit when they rise and suffer when they fall. You go on missions for your patron such as winning a band of outlaws over to their cause, rescuing prisoners from a castle, sabotaging the plans of their noble rivals, or leading their forces when they go to war.