The approach to governance of each country is unique in that rather than being governed directly by the player, each country has a Monarch who is rated for his Military, Administration, and Diplomacy skills. A Monarch's abilities have a significant impact on things like income and diplomacy, so part of the game's planning involves getting the maximum benefit out of the particular strengths your Monarch has at any given time. This extra level of abstraction which forces a player to act through his Monarch adds significantly to an understanding of the reasons for the failures or successes of particular countries in historical scenarios. In addition, a Monarch's reign is limited to a historically reasonable duration, so if you're playing a campaign you'll have quite a few Monarchs. Also, a Monarch's reign can be in a state of Dynastic Crisis or under the cloud of Fragile Health.
Unexpected deaths can throw a spanner into the works at particularly inconvenient times.
As is the case with Imperialism II , trade is crucial, and overseas colonies and trading posts play a crucial part in one's planning. A regime needs money, and much time is spent racing for trade supremacy in various parts of the world. One of the most frequently mentioned complaints about Imperialism II is that it does not properly model the dominant role played by the world's navies and merchant fleets. EU spotlights these units, and your merchant fleets are the key to victory. As you might guess from the above, Europa Universalis is an extremely complex boardgame, running to 70 or so pages of closely-spaced rules.