On steam you can install games ready for when they get released. I’ve just installed Medal of Honour.
It’s supposed to be out in about 2 days, but it’s letting me play it now. I can play single player, and multiplayer matchmaking mode (there are no servers to play on yet).
Is this normal?
Medal of honor came out yesterday 
There was an October 15th release date hanging around in some places, but that was changed a while back, IIRC.
My steam said October 15th today. And when I purchased the game it said ‘this game will be released on 1 day and x hours’ (I didn’t pay attention to the number of hours)
FYI there’s a bug in level 2 - if you fail the hellfire mission first time (I did because I was trying to figure out the controls) it becomes impossible to fire anything. I think you might be able to start the whole mission again (and hope you don’t fail that bit again) to get past it.
I wasn’t going to go through that so I played the MP mode for a bit then turned it off.
I was able to play Civ5 early by using a proxy to fake being in the US, but that was early just for us EU people. 
In the other direction, Steam was actually late with enabling Mount & Blade: Warband so I downloaded the game from TaleWorlds.