The Stanley Parable is the remade/remastered version of the original 2011 mod. It was a collaboration between Davey and UK designer William Pugh, working together as Galactic Cafe. The game expanded substantially upon the mod version, adding substantial amounts of new content, new endings, a complete overhaul of the visual designs, and new voicework from Kevan Brighting.
The game was one of the first to be approved for Steam via the Greenlight community feature. It went on to sell over a million copies, win such awards as the IGF 2014 Audience Choice award, and be featured in schools and museums all over the world.
It can be purchased here.