This manga is written well and builds up a strong world and narrative, but in the end, it just sort of ends without any of that amounting to anything. The plot itself was pretty interesting from beginning to end. However, even though it's a 22-volume manga, not all that much happens because the manga moves incredibly slowly. This is for two reasons. One of them is that it just doesn't have a lot happening per page, with lots of pages that go on random tangents completely unrelated to the main characters or story, or even just random panels showing off the world without any purpose, as well as using larger panels and more panels than most manga do to show the same content. Honestly, this was a bit of a drag even while reading the whole manga in one shot, and I think if I was reading it as it came out it would have been excruciatingly annoying. The other reason is that the manga is much more focused on character relationships within the context of a zombie apocalypse rather than the plot surrounding it. This isn't something unique to this work, rather it's something pretty standard, but I feel this does it to a greater degree than most. For example, the first volume is entirely dedicated to building up the relationship situation set up around Hideo, and the first zombie doesn't appear until the last page of the first volume. There's a point to all this, as we see how these relationships fare in as the zombie apocalypse begins. However, this is over pretty much instantly so it leaves the question of whether it was worth it. That's a recurring theme in this you could say, where relationships take quite a bit of time to build up, but fall apart instantaneously. How fickle everything seems, makes most of the characters unlikable. I sympathized with Hideo, simply because he was the main character and how much of the manga was spent focusing on him, but to be honest he was sort of a jerk too. Nakata seemed pretty cool too, but he wasn't the focus. Rather, the entire side story with people other than those surrounding Hideo felt rushed and random due to not being developed all that much and rather just felt like it was making things slower, especially as when the stories all connected, the effect on Hideo's story felt minimal. Rather, the ending all around felt incredibly underwhelming, in that it felt incredibly arbitrary, resolved nothing, and explained nothing. Rather, it was just suddenly over, and it was completely anticlimactic. Furthermore, it was sad in a way such that I have no idea what sort of point the manga was trying to ultimately trying to convey. There seemed to be some higher-level commentary about unity and hive minds and such, but it didn't feel like it had much of a purpose beyond simply making this different from normal zombie fiction. Similarly, in the end his delusions didn't seem to have much value either. The action was pretty weak. The art was okay.

tl;dr: A character focused zombie manga that's well written but in the end doesn't really say anything.