This game takes advantage of the augmented reality function of the 3ds in a big way. Basically, you wander around (your own home) and look for ghosts - and it's really quite frightening - providing your house is lit up like a Chrsitmas tree! The box says it needs a light area to play in and boy was it not joking - we had trouble finding anywhere bright enough for us to see the screen, and artificial light didn't do the trick (so no playing at night time then - which is a shame as this is a ghost story...)
The main premise of the game is that you are now the proud owner of the Camera Obscura - a camera that can see the spirit world and is roughly the same size and shape as your DS (i.e. it IS the DS). the game lasts rouhgly two hours as you interact with the (provided) diary, solve (not very difficult) puzzles and obviously, fight the aforementioned ghosts!
The graphics are nothing special, and as I say, I spent hours just looking for enough light to play it under.
I have also been slightly spoiled by having a Wii and another game in this series Project Zero 2 - which is far better and doesn't require any off screen antics - I would go for that over this scaled down version.