Fans of Paradox Interactive's flagship franchise will be pleased with Europa Universalis IV, and the few improvements to the nation simulator set in the colonial era are welcome. If you've never played EU before, though, it is easy to get discouraged when you start ruling your nation in 1444 A.D. The user interface is full of useful features, but there are hundreds of rules and bits of information to digest and you'll be hard-pressed to know if the decisions you make will have a positive impact or not. It won't be long before you lose a war, or suffer some other major setback.
That's ok, calm down, don't panic - the joy of EU4 is in the journey. Watching and shaping the alternate history of your nation is exactly the experience the designers want you to have, and EU4 delivers it better than any other game in the series.
EU4 is a real time strategy game in which you control a country from the Middle Ages up until the end of the Napoleonic Wars. You can choose from hundreds of nations to play as - from European powers like England and France to tiny one-province baronies like Orleans. Most of the larger nations have unique properties which aid in replay value. For a great challenge, nothing beats taking a small kingdom like Naples or Scotland and turning it into a superpower, but that will take some serious skill. The AI in singleplayer games is formidable, requiring you to react and grow to keep pace with the larger, stronger nations. There are a few fun choices outside Europe - most notably feudal Japan - but the game is certainly skewed as Euro-centric as the era was. You take over the military, trade and diplomacy of your nation, sending merchants to divert gold to your capitol or annexing territory from your rivals through a royal marriage or conquest. Unlike 4X games such as Civilization or Master of Orion, there are no win conditions in Europa Universalis IV. Sometimes the game gives you missions to raise an army, unite Spain, or kick England off the continent, and these provide fun short term goals, but there's no way the game ever says you've beaten it.
The quantity of different game systems is daunting and discovering how they interact is not always intuitive. A brief tutorial is available, and there's a hint mode that will give short explanations of basic game terms and concepts when you click on the UI, but you'll often find yourself running to forums or wikis to fill in the blanks. For example, the 3 monarch point currencies of administrative, diplomatic and military power are extremely valuable. You earn them each month based on the ruling monarch's stats, modified by many factors such the skills of your hired advisers. While playing I noticed my diplomatic power had a red number, meaning it was negatively modified by something. The tooltip displayed the demarcation "6/4 Diplomatic Relations" but I didn't know what that meant at first. I later learned through the hint system that nations can only enter into a diplomatic relationship with a finite number of other nations - going over that limit restricts the amount of diplomatic power you earn. Europa Universalis IV is full of game rules which are not immediately obvious.
Even fans of the series will debate whether the way trade is modeled in EU4 works well or not. The map is dotted with trade nodes both in ports and inland hubs, and wealth flows through them simulating trade routes. By assigning merchants to the node, you can either influence trade to flow towards your nation, or collect gold from the power you already exert on the node. The trade system is elegant to behold, and it's somehow beautiful to witness the snaking lines of money moving across the map. It's just not very fun. You send your merchants or order your ships to protect trade interests, and that's it. You just let it run.