How are the stories handled? Are they featured prominently?
It's not a linear story-based game. It's an alternate history sandbox.
You pick ANY country from a historically accurate world map of your chosen start date (default and earliest start is 1444) and from there on out, history is entirely up to you and the AI. There is nothing predefined anymore. Though it is surprising and interesting how often many many things tend to move similiar to original history. I think it's a testament to how good the simulation is.
This is the starting situation at 1444:
There isn't even a goal, no way to win the game and watch the credits. You basically set your own goal. World Conquest is theoretically possible, but it's really not the goal of the game at all, and very few players will ever do it. (Managing such a big empire is also not much fun to be honest). What do you want to do? Do you want to play as France and conquer England? Or play as a minor German prince in the Holy Roman Empire and become Emperor and unite the Reich? How about playing as a small African tribe and try to survive against the colonization of the major European powers? Play as the Golden Horde and see how deep a swath of destruction you can drive into Europe? Or play as Venice and try to control all trade coming from the middle east and India. It's completely up to you, it's a pure sandbox game.
The game has achievements that are good templates to go with if you can't decide on goals for yourself IMO. Stuff like owning Paris as England, owning the entire Carribean, making the entire European continent muslim (probably as hard as world conquest if not harder), uniting Japan. In my game I purseued the achievement to own Rome and Moscow - the seats of power of catholic and orthodox christendom - as the Ottoman Empire (after WW1 it become the modern Turkey in case you don't have an idea on who or where that is). Reverse Crusades so to speak. No matter if you pursue those goals or make up your own, there is hundreds of hours of playtime available if you want it.
This is the situation when I ended my game: