The Walking Dead is a very nice linear game cut into 5 episodes. I've only played the 3 first episodes out of 5 because the two last one aren't realized yet, but it's enough to give you my opinion about the game.
Graphics : 4/5 : Very pleasant, and faithful to the comic's.
Gameplay : 4/5 : Command are easy to remember, you don't have a lot of freedom, it's a very linear game, you will have to use both the mouse and the keyboard. (it's very similar to "point and click" games, and sometimes like Shenmue and resident evil concerning the battle system.
Sound/musics : 5/5 : The Ambiance sounds are great! and the musics as well.
OVERALL : 4,5/5 : The 3 first episodes are very quick to finish, but you'll no doubts enjoy restarting the game and change your choices as the game have a lot of possibilities and choice to slightly affect the characters of the game.
The only thing I dislike in the game is that there are not so many possibilities. Your responses don't really change the story (as far as I know) the only choices which may sometimes change is when you are given the choice to rescue one of two characters...
Despite the linearity of the game, I can't help but recommend you to give it a try, especially if you like Zombies game, and the comic and drama of the same name.