Spent 2 hours on it last night, and another hour this morning before work. So far, really enjoying it. There are 3 campaigns to do from what I can tell initially, and I'm currently working through Leon's. It's the same game play style as the last 2 games, but it's gone back to proper zombies, and similar in style to the first 3 games. Quite a few puzzles and a fair bit of searching done so far, so not just a shoot and run game.