This game puts more emphasis on Tactics rather than mindless button mashing "just to kill as many as possible" unlike recent zombies games. 3 zombies at the same time can be a problem, hence, kiting and careful ammo distribution is critical to your survival. All of this coupled with a "Command & Conquer" interface where each of your survivors can be given an order. You can even move the camera to see the horrors that lies ahead and plan carefully.
The atmosphere and the setting is highly detailed, especially the map props. Any fans of George A. Romero's zombies and movies will feel right at home. Heck, the first 2 playable characters are direct cameos of his movies. It's like a big party and everyone was invited.
I haven't tried Multiplayer, but thinking about it makes me shiver... Having "mean" players on your side, hoarding all the guns and ammo, talking trash in the chat saying "he's the boss and he doesn't give a f because it's the zombie apocalypse", closing doors leaving you behind with a horde, shooting you to death because you're bleeding and bleeding in this game attracts zombies... stuff like that... :P
Last note... This game is for hardcore zombie movie/game fanatics only. Only these people may appreciate the great value of this game. That includes me, which is why I'm giving it 10/10.