World War Z - Max Brooks
The Walking Dead Graphic Series - Robert Kirkman
Book of the Dead and Still Dead: Book of the Dead 2 - Skipp and Spector (HIGHLY recommended)
Book of All Flesh, Book of More Flesh, Book of Final Flesh, and Best of All Flesh - zombie anthologies based on the All Flesh Must Be Eaten RPG
Cell - Stephen King (well **I** liked it)
The New Dead - Chris Golden
The Living Dead and The Living Dead 2 - John Adams
And, as a sourcebook, check out
"One of the Living"for the AFMBE RPG. Think of it as a Player's Guide to the Zombie Apocalypse. Tons of "how to survive" advice. Very similar to Brooks' Zombie Survival Guide, only written with RPG stats and ideas. I thumb through it for inspiration all the time.