Thomas Was Alone has sold a rather impressive "over 700,000" copies to date. The game's creator, Mike Bithell, revealed the figure in our first Gamescom podcast*, which you should be able to listen to shortly. The figure comprises PC, Mac, Linux, PS3, and Vita sales, and does not include copies obtained through PS Plus for free. Not bad for a 'rectangle game,' we'd say.
Bithell recently unveiled his very different next game, Volume, which mixes Metal Gear Solid with a dollop of user-generated content. While it's definitely a departure from talking rectangles, Bithell said Thomas Was Alone's narrative roots continue in Volume through a "very strong authored story," and may extend into the game's level creator, since Bithell wants to "make a game that allows people to tell their own stories as well."
*Bithell said "around 700,000" copies on the podcast, but confirmed "over 700,000" after. Technicalities!