Demo came out on Xbox Live last week and i was really impressed with it. Sendit.com has it available to preorder for £10 less than pretty much everywhere else.
Sendit also has the PC version for £16.89 delivered, if that's your platform of choice here: http://www.sendit.com/game/item/6000000004039
Description from Wikipedia:
Overlord is an action adventure game that lets the player control Minions and order them as the player sees fit. In the story, the Minions find the main character in the rubble of the old Overlord's tower, and thus believe him to be a reincarnation of the old Overlord that was killed by the Seven, now corrupted Heroes. These minions, therefore, aid and serve the player loyally as their master. The game will be released in June 2007 on both the PC and Xbox 360. The story revolves around the ever growing Minion armies who are trying to kill the Seven Heroes who destroyed the original Overlord. Since then the Seven Lords have slowly become the living embodiment of The Seven Deadly Sins.
The game is unusual in the concept that there is one main character and a large number of Minions which includes up to 50 to control, though the Nintendo title Pikmin and its sequel used this concept extensively. There are at least four types of smaller minions. The minions include brown minions who do many tasks which include collecting loot. There are red minions that hurl fireballs, which are also immune to fire. While the minions are useful to the player, they are also easily distracted. Distractions may include musicians which need to be killed in order for the minions to resume their productive roles again.