The Stupidest Angel by Christopher Moore
On the week before Christmas, in the sleepy little tourist town of Pine Cove, Santa is murdered. At least that’s what seven-year-old Josh sees happen. In reality, a guy in a Santa suit was having it out with his ex-wife and he fell onto a shovel and died. Not knowing that, Josh makes a desperate Christmas wish, for Santa to be alive again. And then a Christmas miracle happens. At least, that was the plan. Except that heaven's stupidest angel decides to grant his wish by raising Santa and everyone else buried in town from the grave... as brain-hungry zombies.