There hasn't been any good post apocalyptic zombie manga out there since I've finished "I am a hero". The RE series were good but they don't really fit the post apocalyptic part.
Surprised to see it's on-going on 4 volumes... Must have been continued later on, because I'm very convinced this used to be a ditched one-shot. Anyway I liked it back in 2011, good to see it got released eventually.