The AI of this game is absolutely incredible and that makes all the difference in a strategy game. You will have to use merchants to obtain monopolies in global trade centers, form bonds with other kingdoms using royal marriages and even make an oath to protect another country from attack. Keeping your word with other nations enhances your trustworthiness rating to the AI controlled kingdoms and will benefit you in a lot of ways.
The Europa Universalis series of games are all about grand strategy. Thinking ahead a few years into the future and dealing with problems on a global level. All while taking care of the issues concerning your provinces. The third in the series doesn't change much but improves in every area making it another hit amongst serious strategy gamers.