We've left Sgt. Beckett behind (although you might see him around...) and returned to the protagonist from the first game. is there to help you, which brings in an interesting feature of this game...
Apparently, there's a big co-op component, which is odd because why add co-op to the third installment of a series? Well...IF the two characters in co-op are the two from the story, then ok, but it still doesn't make a lot of sense. "I played through two installments of the game, so now let me bring in someone who hasn't?" Hell, an argument could be made that it's a dumb decision from a business stand point as it could mean fewer sales.
Other than that, the enemies are pretty cool with a good amount of mini-boss fights, but the game is pretty linear, so don't expect to be roaming.
The save system is console-ish, but it saves often, so just be sure to quit after a cut scene or a minute or so after a big fight.
Absolutely worth grabbing during a Steam sale for FPS and horror fans.