At the beginning the game is very exciting (especially for those who didn't play Europa Universalis 2). You pick any province you feel sympathy to and start developing your kingdom. There are tons of decisions you will have to make and each of them will sooner or later affect the income/prestige/manpower/piety/etc. This necessity to watch closely many parameters and the consequences of the changes you make is very involving. Add to this that there is no tutorial and you have to use "trial and error" method and you understand why your brain will like this challenging game.
Unfortunately, having an access to the many details of the economical and diplomatical life of your kingdom, you don't have any control over your war machine. For example, being technologically advanced in "Bows" and "Crossbows" it would be logical to have many archers in your army, isn't it (how about "The Battle of Agincourt") ? Bad for you, you can't do it...
Conclusion
If you like economic strategies, check Europa Universalis 2
If you like battles, I guess you better wait for Rome: Total War.