The Early Access alpha of H1Z1 has sold over a million copes on Steam since its launch just two months ago. That figure was reported today by John Smedley, President of Daybreak Game Company, on his personal Twitter account.
The multiplayer zombie survival game launched in mid-January at a price of $20/£15, and is supplemented by premium content such as cosmetic items and airdrop keys. Since then, it's weathered several storms: a shaky launch, controversies over premium items and demands for refunds, and the sale of Sony Online Entertainment coupled with layoffs at Daybreak.
Despite all this, plus the fact that it will be free-to-play when it leaves Early Access, H1Z1 has been a fixture on the list of Steam's top sellers since its launch.