Got this game today, and I must say, it's the most fun I've had playing a game for quite a while. The idea is not dissimilar to Dungeon Keeper, you are an evil Overlord who has been raised from his tomb to lead his minions to world domination, but unlike DK, it's first person, and you only have 'minions', though you have four different types, from Fighters to Flamers, to Ice Minions etc, and basically your horde follows you around the landscape attacking enemies, people, animals, buildings and vegetables indiscriminately at your command. One of the more amusing parts of the game is that Minions will pick up things they think are 'useful', but aren't too discriminating, there's nothing like leading a horde of gibbering maniacs wearing pumpkins on their heads to stop you from being taken seriously...
The graphics are well done, the gameplay is fun, and the voice acting is first class, the minions themselves are particuarly well done.
I'd certainly recommend checking this one out, first impressions are that it's a great game
http://www.codemasters.co.uk/overlord/index.php