There are 31 missions. I am at 27/31 with collecting some easy trophies on normal. I spent 13 hours for it. But i will go for the ''real'' trophies on my 2nd go. You can have fun on this game without doing the missions. So don't make a problem this game's playtrough time.
PSN : WeLoveManti
Games : Prototype, PES 2009, Far Cry 2, GTA 4, Uncharted Drake's Fortune, Rainbow Six Vegas 2, F1 Championship Edition, EURO 2008
PSN Games : Battlefield 1943, Tekken Dark Resurrection Online Bundle