Sorry that this is a bit old hat but I have just got round to playing Series 1 of this and wow what a game! I'm not sure if it will appeal to everyone, it is EXTREMELY story driven and is all about making choices which have ramifications for the rest of the game. It's a point and click adventure, think Monkey Island but with Zombies and less puzzles
I cannot recommend it highly enough, if you check out the reviews for the game pretty much every site gives it 90%+. If you love the series, if you love a good adventure / story game then you should get this game. It's pretty much available on every platform, I have played 3 episodes of Series 1 so far and I am completely invested in the characters and the story. Series 2 is out now and I think so far they have brought 4 episodes out with the 5th due soon.
It's also great to play with my GF as she loves adventure games and the series so quids in from my point of view as I can game all week with her