My favorites so far are world war z and zombie survival guide by Max Brooks. I just bought Patient Zero by Jonathan Maberry, The Living Dead which is a collection of short stories by famous authors such as Stephen King, and Pride and Prejudice and Zombie by Jane Austin and Seth Grahame-Smith.
Give me your take on this books if you have read them.
Also if you have any favorite undead themed books yourself, don't be afraid to share!!!