Europe is in turmoil. The lands are fragmented into petty fiefs, the emperor struggles with the Pope, and the Holy Father declares that all those who go to liberate the Holy Land will be freed of their sins. Now is the time for greatness.
It's a really great game. There is a lot of DLC (21 items!), but most of it is cosmetic. The big ones you will probably want:
Sunset Invasion (Aztecs invade! (Ahistorical))
Legacy of Rome (Byzantine stuff)
Sword of Islam ( lets you play muslim rulers )
The Republic (lets you play a trader)