IL-2 Sturmovik: Cliffs of Dover is 40% off at Get Games for 48 hours only. It says that Steamworks is required for multiplayer only. Not sure what that means exactly. I’m guessing you can play single player fine on your computer, but if you want to play online you’ll have to activate the cd key on Steam. Don’t quote me on that though.
IL-2 Sturmovik: Cilffs of Dover = $29.99 / £20.99 / €29.99