Buy this game in preparation for AP World History. Try to find another game with that sort of endorsement.
The scale of this game is just disgusting. It really is. More historically accurate than Rome, better looking than Shogun, and you can buy it now for an entire $10 in most stores. The descriptions of eras, factions, units and historical events are simply good reading, and a lot of the stuff I absorbed (Through several months worth of osmosis) was used a few years later to completely slaughter AP World History.
The gameplay, based upon a 2002 standard, was unmatched. It improved upon the fundamentals of the Shogun engine by adding ships, new agents, and a somewhat poorly executed but interesting religious system. Occasionally you will lose a few units behind banners, and sometimes you will unintentionally drop units onto neighboring territories, but there is a screen that warns you that you are about to trigger a major war. A nice fail-safe. The battles, with your units set to maximum, your resolution up to 1280x1024, and all of the effects set on high...are not the most impressive things you may have ever seen (Especially if you have been picking away at Rome). But the camera functions quite well, able move almost unrestrictedly in three dimensions, and your units are almost always responsive to your commands.
The sounds of battle are done quite well, for an older game. I would give an 8 here, but it receives a 9 for one sound in particular...when killing your captured soldiers in battle (The ones you can hold for ransom), there is perhaps the single best sound effect ever utilized in the history of video games. Somewhere between crushing bones, slitting throats and the helpless cries of men being slaughtered, you start to realize just why this game is a masterpiece.
And value? Crap. You will beat the Grand Theft Auto trilogy TWICE before you have seen everything this game has to offer. Each faction plays a different game, and with the option to fast-forward time a few hundred years you can play shorter games if 1087 to 1453 sounds a bit too epic for you. And the four difficulty levels should also keep you busy.
I complained about not being able to play as the Argonese, the Hungarians and the Sicilians at one point. And then I found Viking Invasion and got my junk tossed. And you can get both Medieval and the expansion for about $20 now. $20 bucks for months and months of slaughter, and frankly a great history lesson. Buy it.