I found this in a bargain bin years and years ago and bought it on a whim. Other reviews have already said it better, but this game (and its sequel) take your average RTS mechanics and tie it into a fairly complex ecosystem and economy. Cities will slowly grow in population, from which you can recruit troops and people to man various structures. Those structures in turn create the backbone of an economy and a military. Need to build up some cash? Build a factory for a town. Just know that each person working in that factory is one less sword for your army. Soldiers and cities grow over time in experience and usefulness and each has its own loyalty to your cause. Do things to increase that loyalty and they will be more effective to your empire. Break the loyalty of an enemy's troops or towns and watch them be torn apart by their own men. I love these games (they're easily my favorite real-time strategy games from back in the genre's heyday). The screenshots aren't really a strong sell, but each time you play is a layered, unique experience, and you can do far worse than pick these up and give them a try.
As a ancillary note, I haven't tried playing any of GoG's games multiplayer (so I don't know if it's possible here), but me and my brother used to have so much fun playing these games together. Having the unpredictability of other human players to ally with (and double-cross) makes for some very interesting scenarios.