Frankly, this rocks. The creation of magic items is also given the same treatment. Combat with hand to hand weapons is relatively simple considered to the rules on magic but given that mages are forbidden to figt other mages unless a duel is formally announced, this is to be expected. This is again a masterful innovation. AM gives you a pretty good background on the ley of Europe and the various realms.
Realms are various other powers beside magic.
Magic behaves differently in these different Realms. There is the Faerie, Mundane, Divine, Infernal. As one can guess, they talk about magic and what it can and can not do while in these areas of power controlled by faeries, the church and demons. All in all, one can not go wrong with Ars Magica. Frankly, this is one of the best RPGs I have ever seen.