Final Liberation: Warhammer Epic 40,000 is a computer adaptation of the Games Workshop tabletop game of the same name. The planet Volistad has been conquered by an Ork invasion force, and it's up to the Imperial Guard regiments and a Space Marines chapter to free the planet and end the Ork threat.
The single player campaign is played on a strategic map of Volistad split into different sectors. Players move armies from sector to sector, and when an army enters an enemy-occupied one, a turn-based battle is played on a tactical map. Captured sectors give resource points that can be used to buy new units and build new armies. The goal is of course to free the planet and eliminate the Ork presence.
The game is faithful to the Warhammer Epic 40k universe. There are only three armies available (Imperial Guard, Space Marines and Orks), but each has the same units and organization as in the tabletop game: the Imperial Guard has several famous regiments, lots of vehicles, titans from the Adeptus Titanicus and the Orks forces can field an impressive array of strange vehicles.
The game also has a multiplayer mode which allows up to four players to build a custom force and battle it out on a tactical map.