I've always been a big fan of this game, hoping sometime there would be another sequel, but it seems the idea was dropped. To give you an idea of how much I adore this game, I've played through it about four times by this point.
There's always question about which Overlord you should pick up if any, the first or the second? Personally, I say both. Here I will just review the first one though.
A fantastic singleplayer RPG with clever humor, good boss fights, enticing story and an interesting combat system that I can't say I've seen in any other game.
You are the Overlord. Your job is to restore your tower to its former glory, convince the lowly townsfolk that you are indeed the Overlord and to wreak havoc with your minions (although sometimes you might decide to be nice to the citizens of your domain to make them praise you rather than fear you)
But what is an Overlord without his minions? There are four types of minions, which you unlock over time, but pretty early in the game you have all four. The first type is your default melee minions that just love to get in trouble and start fights, the second is a ranged type that are terrible in melee but can put out fires and throw fireballs, the third is a sneakier kind that can be used with clever positioning to take out key targets rapidly, but they suffer in direct confrontation, and the fourth is a healer that can resurrect your fallen minions for a while before their corpses decay (They can also swim, unlike all your other minions)
The overlord himself of course also has combat potential. He can hit people with his melee weapon of choice and cast spells that he has unlocked, there are plenty of spells ranging from direct damage (throwing fire at all your enemies and watching them burn to death while laughing horrifically) to buffing your minions (and watching them claw your enemies apart in a maddened frenzy before they start tearing each other apart)
There's also a crafting system that lets you craft weapons and armour with special stat bonuses given by letting your minions throw themselves into the flames to enhance your equipment.
This is definitely one of the most overlooked games that I know of, and that couldn't be a more undeserving title to have.