It’s just been announced that Left 4 Dead 2, Valve’s follow-up cooperative zombie shooter, has reached over two million units sold in the two weeks it’s been available at retail.

According to Valve, the comparative sales performance of the game is more than double that of the original Left 4 Dead which released exactly one year before its sequel, benefiting from Thanksgiving ‘Black Friday’ sales promotions in North America.

VP of marketing at Valve Doug Lombardi beamed:

“Left 4 Dead 2 is off to a great start with strong support at retail and great reviews from the press. Meanwhile the title has already been played by over 1 million Xbox LIVE Gold account holders, and news regarding L4D2 DLC 1 is coming very soon.”