Cowboys are cool, Zombies are cooler, if you mix them together you get the coolerist thing ever! Red Dead Redemption is a great game with plenty of extras and a great story. When you finished the game it left you wanting for something, and that thing is zombies. Undead Redemption adds a great extra flavor to a game that was great anyways.
Get this DLC on Xbox for 800 points or $9.99 on the PSN. The replay value is unfortunately low, but the time you spend playing is well worth the cost.