As I told my wife several years ago, or, rather, as she told me when I was writing the initial test stories for Cities of the Dead, "zombies are popular, now." Indeed, they are, and SyFy (I hate that and prefer SciFi, but the channel has almost no science fiction on it anymore) is coming out with Z Nation in September. I assume the reason is because The Walking Dead has made it five seasons and is continuing to grow in popularity.
With any luck, Z Nation will be better than TWD, and I say that as a fan of the latter. However, TWD is a marginally decent show about zombies per episode, but as a series, it tells no compelling stories. The story arcs are lame, and most of the characters are unknowable and unlikable. But, zombies!
Now, this is true with just about every zombie TV show or movie: the writers don't know what to do with the material on hand, so you just get zombies and people shooting them: zombie pron. This can be entertaining, but it's usually frustrating, too, since what you're really dealing with is a post-apocalpse scenario in which the real story is how the humans living create a new civilization amid the chaos. This is what I attempted to address in CotD, showing how mankind struggles to survive amid the new landscape where most of the "people" are now zombies, not just stories of people killing the undead (though there is plenty of that).
My book was looked at by a movie/television producer shortly after it came out, but he said he couldn't figure out how to make it into something (that's the short-short version, since he told me this through a mutual friend before I had even thought of how to translate it to live action). I could easily turn my stories into a television series, if ever given a chance. Not sour grapes, there, just noticing that I've had time to think about how my 20 different stories - which tell one complete story - could be altered to a different medium.
And, yes, I have written some more zombie stories for a possible second CotD book, fleshing out (heh) some of the original stories with follow-ons, as well as some new stories which look at issues left out of the first book. I may keep at that in my spare time (I'm currently working on the third Divine World installment, so...), but my spare time has many suitors these days.
And that's about as deep as I'm going to get with this today.