Dead Space is exactly what it tries to be, an immersive survival horror with a AAA budget. It feels like Resident Evil 4 in space done properly. Except it isn't campy in the traditional Resident Evil sort of way, although it does borrow similarly wonk over the shoulder camera angle and the controls suffer a little for it.
Atmosphere is the name of the game. It is done very well. From the amazing audio to the well done small visual details such as holographic displays here and there around the ship. Even the weapons fit the story line. The methods needed to take down enemies is a nice change of pace. There are nicely veiled instructions when you are going to need to know something.
There are puzzles to solve occasionally. None of them are overly difficult. The occasional predictable monster moment for survival horror veterans, but overall it does a great job.
I paid $5 on a Steam sale. I stole this game for that price. If I had paid $30, I feel I would have gotten my money's worth. It is worth the current $20 price tag. Being 6 hours in, I understand I am roughly 25% of the way through playing, from what I am told, just adds to the value.
I don't want to tell you too much about the plot as to not give anything away. All in all jsut know that I am enjoying playing it and it is worht picking up, especially if you see it on sale for less than $20.