It's the first draft of a really great novel
Monster Island began life as a serialized novel on the internet. It then made the leap to publication, surely one of the few such online novels to do so. As such, I'm sure it has given new hope to millions of not-traditionally-published authors. But having consumed more than my fair share of serialized, podcasted, and otherwise internet-only fiction, I was able to see the flaws inherent in the medium all too clearly.
Serialized internet novels are, in a nutshell, first drafts. You are essentially reading it as the author writes it. This gives a wonderful sense of immediacy for readers who are reading it as it is posted. And it's considerably easier for the author, who needs only to write their novel once and be done with it.
But still: it's a first draft. This means that it sucks. Not because David Wellington sucks as an author, but because all first drafts suck. That is, after all, why we call them "first drafts."
So it feels churlish to criticize Monster Island's many faults, because they are the faults of a first draft. It's just a pity there won't be a second or third draft, because I bet that would be a pretty amazing book. And word to anyone looking to bring their serialized internet novel to the publishing world: please don't publish it as-is. Treat the original version as your first draft, and revise accordingly.
There are many wonderful set pieces in Monster Island. But they were, for me, overshadowed by how nonsensical the rest of the book was. No explanations are given for anything. Everything happens essentially at random.
We don't know why Somalia has somehow been spared zombification, why only a UN inspector can save us, why he has to travel across the Atlantic by boat to fetch drugs from Manhattan, why he is accompanied by teenage girl rebel fighters, why why why. There is no "why." Whenever Wellington writes himself into a corner, he ends that chapter and switches to the alternate narrative. It's a great trick for the online format - I've done it myself - but again, it's a trick that belongs in a first draft.
Also, one final note, as long as I'm kicking the dude while he's down: he, like many male authors, makes the assumption that women pee out of their vaginas. This is incorrect. (Just one of my pet peeves…)