If you're having trouble playing Shogun 2 right now, you're not alone. A patch that was released in the last hour has just locked out what appears to be the entire playerbase. Currently, if you try and start the game, you'll be confronted with a Steam error message: Incomplete installation of Total War: SHOGUN 2 (15). A long thread on the Steam forums suggests that it's not an isolated problem, and CA have already said they're aware of the issue .
That doesn't stop it being phenomenally irritating.
UPDATE: And it's fixed. That was ridiculous.