Well I got the game last night and played for 3 hours (before having to go to bed at 2 AM!!)
Brilliant, it's what I wanted and more. 3 hours in and I've yet to even hold a gun. The story pulls you in for hours at the beginning as you investigate around, slowly but surely coming to realise that you may be in WAY over your head on the case your investigating.
The immersion level is top notch, with no HUD clutering up the screen you really get drawn into the game. Sanity effects also creep you out, peering over a ledge induces a bit of vertigo, blurring your vision and making you dizzy.
Seeing dead bodies (or other things you shouldn't want to see on an average trip to a cultists abode) get your heartbeat racing, the joypad vibrating and your sense of dread up.
Your character can be pushed over the edge, start hearing voices in his head - and if things go too far, he could take his own life.
Graphics and sound are top notch - the atmosphere that the dark brooding graphics and sound create are fantastic, drawing you into the 1920's New England era.
It's an adventure/first person game, with elements of FPS later when you find (and need) some guns to defend yourself. It gets to the point where the NPC's in the game have had enough of your snooping...then all hell breaks loose.
If you have an Xbox, and want a different gaming experiance from all the 'kill everything in site' FPS games out there, I highly recommend it.