Ruined by AI stupidity and sheer number of buggs. Politics exists but has no impact on the game, trade is too simplist.
AI is so stupid that forgets to build units above tier 1, get stuck in a loop changing formation, forgets that he is attacking and sit and wait until time runs out, attacks your settlements with no chance to beat even the garrison, can't manage his economy.
Naval battles are worst in the Total War series, ships are very hard to maneuvre, boarding takes very long and sometimes get stuck making melee ships utterly useless. Disembarking is a TOTAL gambling (not WAR), you might end up with troops stuck on boats.
Battles are very short due to morale that breaks soo fast. 5 min is a loong fight. Troops cheer too much and forgets to fight after they won a minor encounter, while around them hell breaks loose. Formations are only for visual show, they matter not in a fight, enemy pass through with ease making impossible to hold a front line and there goes the strategy factor. Night battles should prevent reinforcing as intended, they don't. In tortoise formation you arrive near wall/enemy with less troops than if you would simply run to cover the distance.
Balance issues: troops get experience very fast, same the Generals. Time in years/turn goes so fast that you don't have much time to use that 7 stars General. They pass away fast and because your elite troops replenish without a drop in rank no matter how many soldiers were replenished, you end up having a noob General on a very high skill army that has so high morale on his own that it has no need of a General anyway(but you cant move an army without a general). Replenish is too fast even without traits.
Siege is stupidly designed. It takes less time to break a gate with troops by setting on fire than with siege rams, and for siege rams you need to invest in tech research to build them when lay siege.
Strategic positioning on the battlefield is dead because Creative Assembly force you to defend a flag point in the middle of a field exposed from all the angles. Sun Tzu must turn in his grave.
There are so many more bad things but it becomes boring even to criticize so let's get to positive things.
Campaign map is huge and looks good. Recruitment system is new and spare you from micromanagement to gather your troops on campaign map.
Diplomacy is better than previous titles, even though can became frustrating when friends near you don't want to trade with you, you must learn that discovering more factions on the map will give you plenty of trade partners, if you have some strategic resources in your pocket. At start you can't rush in alliances, you need to build your reputation a little more (as reliable and trustworthy) and to become more powerful, then you will have whom to talk to. Province sistem with more settlements is nice but more info on how buildings work and what affect is needed.
Visually the battle looks very good. Line of sight mechanics is useful for ambush with cavalry which brings something new to the game, too bad the AI screws they joy of victory.
In the end, shame on GS for the review they made on this game. After the review on last Simcity i thought they have the balls to do it right. My bad.