If you secure your copy before the deal ends, you'll receive an email with a Steam code you can redeem to add the game to your library. Note that you have to redeem it before September 15 for the code to work. Once you do, though, the game is your to keep forever, even if you unsubscribe from the newsletter. (And don't worry if you're already subscribed; you can still get the game for free).
Warhammer 40,000: Space Marine is a third-person shooter from 2011 that's set in the tabletop game's apocalyptic distant future. You play as an Ultramarine, a super soldier whose job is to blast, chainsaw, and generally eviscerate hordes of Ork enemies.
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Source: GameSpot
