Reviews: Crusader Kings

Difficult, but Awesome

This game doesn't have a learning curve so much as the Learning Cliffs of Insanity. You will spend at least a few sessions getting your ass kicked by bigger realms, and the tutorial isn't good for much besides explaining some of the basic principles. This is not a game with an easy mode and you need to think creatively and plan ahead.

BUT! Once you really know what you're doing and have good people at your back (free hint: Jewish councillors, they're good deals for Christian and Muslim rulers, especially if you can convert them to your religion to negate the infidel opinion penalty), you can slowly turn your (for example) two-county tribe in the ass end of Scotland into a world power, and even carry it over to Europa Universalis IV if you play long enough. It's addictive as hell.
http://tvtropes.org/pmwiki/reviews.php?target_group=Videogame&target_title=CrusaderKings