Well i couldnt tell you exactly how it plays, because i havent played it! What i can tell you is based on trailer footage and a little preview i read during my break today in OPS2 (I think thats what its called!).
The game involves mainly 2 things, walking/running around, and shooting (What else do you need eh?). These are 2 completely different styles in control though. WHen walking and running, the camera moves into 3rd person and makes walking and running around seem very film-esque, too add to the feel of the game. Shooting however, the camera changes into first person and plays like Old-School FPS games, where you see the tip of the gun and a laser pointy thing to see where your ammo's gonna end up (I assume you can turn it off though if you're daring enough!), almost like a light gun game... except without the light gun capability!
What seems cool though is when you kill a guy after shooting him to death, he almost implodes and blood is sprayed everywhere (Not that im like a fan of massacres or anything

). It seems at first though you use this blood to collect and then deposit in certain places to unlock more personalities, as only few are available at the start of the game. When you get further into the game, you use the blood you've collected to visit a certain person dotted around levels wearing a mask (Similiar to Resi Evil) who will trade it for more goodies (I'm assuming weapon upgrades, etc.)... except to get his business you have to shoot him in the mask, prompting him to show you the middle finger, and then get on with some trading (As in the image in the post above!). Each enemy has an 'instant kill' spot, but its very hard to hit, and evolve, i'm guessing sort of like Resident Evil 4 (Again)... except without the inside claws slashing you to death when you blast a head off!
Also, when you're running around and come to a junction, the game turns to a menu and glass shards appear on the screen asking you which direction you want to go (I.e. Hall, Lounge, etc.). You can also change your personality at certain times in the game through a menu to help you get through a certain puzzle.
Continuing on from what i've read and remember, the bosses are something completely different. Im talking monsters you've never even considered before, such as monsters you have to chase around a maze, and monsters with huge brains (Aparently about 20 feet of it hanging out and being dragged along the floor!!!).
Also, this game is VERY adult-natured. For example, the main character this game is all based upon, is a lunatic in a mental hospital who, according to his imagination, has a very sexy nurse indeed... that likes to do.. you know... stuff... to him... but they didnt show any screens of that in the magazine!
Hope that answers some questions about gameplay!