Do you remember the primitive empire building mechanics in Mount and Blade? Ever feel like they weren't able to cover the real breadth of possible political intrigue? Did you ever think you could have solved a standoff by quietly assassinating a regent, marrying off your sister to a mongolian despot, keeping a rival monarchs heir under lock and key by offering to "educate" them before declaring a surprise war or carefully replacing all your precursors council members with men fiercely loyal to yourself?
Then step right this way my friend, as Crusader Kings 2 is essentially ALL that and a metric tonne more.

On the positive side Crusader Kings 2 is one of those games that benefits from a level of detail that should impress even the most brick-chewing and hardened history buff as the majority of its campaigns are based around the monarchs and clergy of the real middle ages. Paradox has done a laudible job in recreating the insane game of political backsies that these historical figures found themselves living through or dieing in. The fact that it also gives you a quick and easy way to look up more information on particularly interesting characters is a great example of tangential learning used in gaming. Further to this there's a truly dizzying amount of depth to the games mechanics that gives you an idea of just why every ruler had to have a retinue of advisors and counsels to help them manage information and make decisions. The lack of a strong structured narrative also gives the player a lot of freedom in how they tackle problems or exploit oppurtunities. It leads to some rather interesting emergent gameplay scenarios that I suspect people who enjoy the game while love swapping with other players just to compare how they each dealt with unexpected problems.
It all adds together to give CS2 a real sense of atmosphere, refreshingly not in the usual "dark, rainy and miserable" sense that highly atmospheric games often default to. You end up feeling like a man (or woman) with a bit of power under their belt but an order of magnitude more responsibility than you could possibly have been prepared for.

On the other hand...the user interface and tutorial could use a hell of a lot of work. Yes this is fairly par for the course in a Paradox game but it becomes more of a bugbear than usual in CS2 due to the sheer magnitude of information the game is required to communicate to the player. You open a single figure's profile and you're given their nationality, general skills, specific strengths and weaknesses, religion, marriage/betrothal status, claims to land and title, demense makeup, alliances, honourary titles, family tree, dynastic tree, vassals, retainers, your opinion of them, their opinions of you, their hopes and dreams...AGH! STOP! Look I just want to know who his heirs are so I can kidnap one of them!

Compounding this problem is that the number of possible avenues of play is quite large and, while the tutorial does it's level best to introduce us to all of them, it felt like trying to teach the specifics of circuit design to a confused panda: More difficult than nessecary and ultimately kind of pointless. When I sat down to go through the tutorial myself I had already initiated and succesfully resolved two murder plots by the time the game actually introduced me to the plotting and conspiracy system. Yet by the time my neighbours were marching over my home territory and I was running about in a flap trying to route them the game decided that now, after the invasion of my home had already begun, would be a good time to teach me about building static defences...on my island colony several thousand kilometeres away. Thanks CS2, you couldn't have mentioned this whole "developing technology" thing a little earlier? Perhaps back before my paper thin walls had been breached by a ballistae?

Ultimately though once a player works out the ins and outs of the system, and yes that might take several decades of PHD level research and a small team of interns working around the clock, they'll find themselves immersed in a mechanically deep and highly immersive world that will reward them with... well probbably a poisoned cup of wine carried by your heir apparent but a historically accurate one nonetheless.