From the publisher website:
Learn the Secrets of the Magi
Houses of Hermes describes the twelve houses that compose the Order of Hermes, their origins, their histories, and their recent actions. It provides important and dynamic information for players and storyguides alike, adding detail and drama to any Ars Magica saga. It includes:
* A plot connected to each house. Each plot is grand enough to serve as the focus of your troupe's saga.
* Story ideas for each house, for shorter-term play. These ideas bring the natures and styles of the various houses to life.
* Sample magi who can serve as the player characters' masters, as non-player character in your saga, or as models for mid-level magi.
* New spells and abilities representing the houses' differing specialties, including faerie magic and the special spells of the quaesitoris.
* An in-depth treatment of apprenticeship, from the apprentice's and master's points of view.
* A record of the Order's history, from ancient times to A.D. 1220, including the crises that have shaken the Order and the growing threat from mundane civilization.