The best 'serious' strategy game released in a long time!
It does take a while to learn the nuances, especially if want to master both the military and political side. You can get AI ministers (advisors) to take over any part that you don't want to do, but if you leave your military planning with the AI then you'll get a very defensive strategic approach.
Since scenarios are quite good, and the campaign (where you start as a single small region and move up to take on the rest of the world) is a lot of fun (though don't expect to finish a campaign quickly!)
There have also been a lot of updates with new content released the past few months - some great new missions, and also a new 'United States' scenario where most states are represented as separate regions (so you can truly take on a Battle of the States in a single map). This US scenario is lots of fun - and sometimes Mexico and Canada even get involved!
It's part wargame and part world-domination strategy game, but it puts it together very well - a lot of fun if you take the time to learn it!