Well i got CKII about 3 months ago. At first found it really hard to get into. However I pursued (read a lot of guides and watched a lot of youtube vids), as I invested in all the dlc's.
That said, I am glad I didn't put this game down right away and instead pursued because the game in its complexity is now very addictive. For anyone that hasn't played this, let me just say it is nothing like total war type 'point & click' on a territory to send ones army and conquer game-in this game you firstly need a Casus Belli (a reason to go to war) and meet a bunch of other prerequisites prior to being able to conquer a territory (albeit one can always raid/loot other territories without a CB).
With the many counties/duchies in any given kingdom it also becomes an internal struggle as you come toe to toe with the other counts/dukes etc. so depending on kingdom 'centralisation' you can often find yourself conquering territories within your own kingdom, joining coalitions within your own kingdoms against the king or opposing coalitions etc. (this is medieval ), and just generally trying to make your way up the ranks; even trying to become king yourself if you want, before even beginning to focus on foreign kingdoms (of course for an easier campaign one can just play a king to start with-I'd recommend this for anyone new to the game).
Then there is the crusading aspect in between all the chaos (if youre a Catholic faction, jihads for Muslims etc.).
Let me just say, it is also not just about warfare, playing as a Duke I managed to lower the crown authority, had the King imprisoned, and while at it banged and impregnated my Kings wife (the queen), who had my son. That is just one example of the crazy , besides expelling the Jews one can get up-to in CKII
Lastly, the ability to make one's own custom characters (with the ruler designer), is also neat.
Sadly I think most newbies will put this game down due to the initial complexity of the game, but those who don't will be rewarded. After 200+ hour I have now developed the 'addicted to CKII' trait.
end of my ramble...