When this was released I was impressed at how different it was to the standard first person shooter. The controls may be essentially based on Call of Duty but this one has really fun elements thrown into the mix. Right from the beginning you can tell that the game is trying to be scary by knocking over items around you occasionally and flashing images etc (knowledge of the games predecessors is advisable but not 100% essential) all supposedly to make you jump, all written in the script. It doesn't exactly creep you out but nice try. The fact the campaign is essentially co-op is a decent idea. 2 characters available, both quite different to suit your style. You've got the guy who doesn't say anything and puts everything in slow-motion, acquiring all kinds of fire-arms and generally beating any opposition in the face. Then there's his demented brother who uses the bodies of enemy troops to do his bidding, using psychic powers to hold and throw enemies. It is particularly fun in my own opinion to steal and gib/self-destruct the body you are in, especially after the cheeky, snigger laugh from your character as he steals them. It never gets old.

Enemies range from your standard swat team with assault rifles to super soldiers with teleporting capabilities and demons who like to play with knives. Game environments also vary quite well featuring; broken down houses in suburbia, decrepit derelict factories, dusty shadow ridden cowboy towns, large real life monument bridges with large scale mech battles. The story isn't that fantastic but there are decent cut-scenes, good maps and generally fun gameplay with the gradually tougher and varied enemies, newer weapons and even giant mechs to control. Level review is a nice touch as well, revealing who got the most points, levelling up by completing the accomplishments and being dubbed the 'favourite son' - points are gained by completing tasks and meeting prerequisites within levels such as using specific abilities a number of times, finding and sharing/stealing souls/points from dead bodies scattered throughout all the levels - to encourage gameplay variety.
So its not really scary that much (apart from perhaps inside a factory during a blackout when you get mobbed by numerous goblin guys wielding butcher knives) , you don't 'really' need to have played the first two games and its a fun alternative to the standard first person shooters being released non stop.