Different style to his other films? (EG: Seven, Fight Club)

It's not different, it's exactly the same. It deals with lonely outcast and/or socially awkward people. It deals with people in denial (main characters especially)

As for the style, it is exactly the same. Low key lighting, quick cuts between scenes, especially this film and Fight club.
The entire movie is on steroids. A lot of talking in it, again this an fight club.

Generally, Fincher is making the same movie again and again and in the only way he knows how. (i don't know if you've seen it but) Gone girl=Zodiac and panic room (suspenseful and police procedure)=seven (police procedure, someone toying with protagonist in a dark way)=the game (someone toying with protagonist in a dark way)=girl with the dragon tattoo (someone toying with someone in a dark way i.e the big mystery, sending of flowers each year)=the social network (both are hackers, friendless, and if you watch closely TSN, Mark even shows signs of homosexuality). so what's left Curious case. Do a study on that one, it's the most different as far as story and so style. It doesn't suit to do quick cuts, or boisterous music as he does in the others as the story doesn't call for it, and the main character was born an outcast and so different, and it's not chosen or desired.

Evil Dead 2...