Heres what i have right at hand, granted its not my complete collection.
Cell by Stephen King- While not really a zombie story per say those infected by the strange signal do exhibit some zombie like characteristics.
Eden by Tony Monchinski- One of the Permuted Press published zombie books. Takes place in a fortified compound in what used to be Queens, New York that the survivors have named Eden. I just pourchased this book and am about to start reading it.
Zombie Survival Guide by Max Brooks- No explination needed since most of us already know of it.
World War Z: An Oral History of the Zombie War by Max Brooks- Again another book by Max Brooks that should need no explanation.
The Zombie Survival Guide: Recorded Attacks by Max Brooks- A graphic novelization of some of the zombie outbreaks from history that are found in the back of the Zombie Survival Guide.
Patient Zero by Johnathan Maberry- Already recommended by others.
Twilight of the Dead by Travis Adkins- Another Permuted Press published book.
After Twilight: Walking with the Dead by Travis Adkins- Another Permuted Press published book. The sequal to Twilight of the Dead.
History is Dead: A zombie Anthology published by Permuted Press.
The Living Dead published by night Shade Books. A zombie anthology, it contains stories from a good number of authors including Stephen King and Clive Barker.
Season of Rot by Eric S. Brown, Another Permuted Press published book. This one contains five zombie novellas written by Eric S. Brown.
U.S. Army Zombie Combat Skills published by Lyons Press. This book is supposed to be a Department of the Army manual on how to combat zombies. A good number of the illustrations in it are actually from Military manuals, though they have been modified some to have zombies, warnings of zombies, etc... in them. The weapons and equipment pictures are a good example of modified images, they use actual military document images as a base then they added "custom" paint jobs to the equipment such as a flame paint job on the M240B machine gun image or the words Eat Flaming Life!! being painted on the barrel of the M72 LAW. The actual content of the book has been drawn from real military manuals, though they have added the zombie aspect to the material, other then references to the Undead in the book it looks to be almost all factual information. I have only skimmed it and did quick comparisons to some of the actual US Army Manuals I have.