I wrote down all the books I could find in the store, and several I found on the computer system. Despite that, I'm sure I'm missing a lot of books. Feel free to add titles you know of in comments and I'll edit them into the list when I'm back from Japan. I also didn't originally plan to add forthcoming titles, so again, I'm sure I missed some.
The Living Dead – John Joseph Adams, Ed.
Dead End, * Dead History, * Dead Worlds, Love is Dead – Anthony Giangregorio, Ed.
The New Dead – Christopher Golden, Ed.
The Dead that Walk – Stephen Jones, Ed.
The Best of All Flesh – James Lowder, Ed.
My Zombie Valentine – Katie MacAlister, Angie Fox, Marianne Mancusi, Lisa Coach
Zombies: Encounters with the Hungry Dead – John Skipp, Ed.
Just Before Night – Joe Tonzelli, Ed.
Jailbait Zombie – Mario Acevedo
Pride & Prejudice & Zombies – Jane Austen & Seth Grahame-Smith
Tomes of the Dead: Way of the Barefoot Zombie – Jasper Bark
Reign of the Dead – Len Barnhart
Brains – Robin Becker
Tomes of the Dead: Tide of Souls – Simon Bestwick
Day by Day Armageddon – J. L. Bourne
World War Z – Max Brooks
Play Dead – Ryan Brown
Breathers – S. G. Browne
The Lifeless – Lorne Dixon
Empire – David Dunwoody
Dead Bitch Army – Andre Duza
Happy Hour of the Damned, Battle of the Network Zombies – Mark Henry
Pride & Prejudice & Zombies: Dawn of the Dreadfuls – Steve Hockensmith
State of Decay – James Knapp
Dead House – Keith Luethke
Stupidest Angel – Christopher Moore
* Boneshaker - Cherie Priest
It's Beginning to Look a Lot Like Zombies – Michael Spradlin (Christmas Carols)
Zombies: A Record of the Year of Infection – Robert Twombly
Monster Island, Monster Nation, Monster Planet – David Wellington
Zombie Queen of Newberry High – Amanda Ashby
Zombie Blondes – James Brian
I Kissed a Zombie, and I liked it – Adam Selzer
Never Slow Dance with a Zombie – E. Van Louve
How to be a Zombie – Serena Valentino (July)
Generation Dead, Kiss of Life, Passing Strange – Daniel Waters
For the Love of the Dead: Gay Zombie Erotica – Hal Bodner (June/Jan? - I'm finding conflicting information on its release date, perhaps due to regonality)
Ten Little Zombies - Andy Rash (July)
Married With Zombies – Jesse Petersen (Sept)
Rise Again – Ben Tripp (Oct)
The Ravening – Stewart Sternberg (Nov)
War of the Worlds, Plus Blood, Guts & Zombies – H. G. Wells & Eric Brown (Dec)
* Thanks to Matt for posting these additions in the comments.