I recently bought Dead Space on Xbox 360 (great game BTW) and decided to get this to give me some background on the story. That's exactly what it did! The story acts as a prequel to the game and explains how things came to be, right up to the point were you arrive at the ship in the game. I'm not really an anime fan so at first I wasn't too impressed with the way it looked, but it did grow on me as time went on. As a Blu Ray disc I'm giving it 4*, some of it looked amazing, other parts pretty ordinary.
If you own or are planning to buy Dead Space the game then I recommend it, similarly if your an anime fan I think you'll enjoy it. If your not buying the game or not into anime then I wouldn't bother.
PS - I also recommend downloading the animated comics from xbox live as they add a lot to the story. They are esentially a prequel to the prequel and explain a lot!