This is definitely a deviation from the previous three novels in this series - although the whole series is supposed to be sci-fi horror/thriller, this one is so far the only one that I think really fits the horror genre.
While the previous three books focused on Victor Frankenstein, and his 'New Race' set to wipe out humanity, the collapse of that empire, and the people in New Orleans who worked against him, this book is set 2 years later.
Victor's clone (who sees himself as more intelligent and rational than the original Victor) has established himself in a small Montana towns, and the novel starts as the plan to eradicate humanity gets underway. We see the return of Deucalion, Carson and Michael, and Erika and Jocko, teaming up together once again to try and stop Victor.
The book is the start of the apocalypse, seen from the point of view of the main characters returning from previous books, as well as a few new ones - on both sides of the war.
Deucalion is the same as ever; steadfast, determined, unmoving in his desire to remove Victor from the world and keep humanity safe. The small glimpses we get of his internal thoughts - the love and wonder at the world, his outrage at the people hurt and killed by Victor's army, and the fierce protection he feels towards the earth - I'd love to see so much more of it. He's an enigma, an impossibility, and I desperately want to know more about what brought him to life and what will happen to him afterwards.
Carson and Michael are now married with a child, which does feel like a weird shift from them being determined to ignore their feelings from each other - but considering we knew what their feelings were, the time skip of 2 years is enough to make it feel realistic and reasonable too. Their banter and demeanour is still the same, which is fun, although their thoughts are now consumed with their daughter and how they can give her a good world to grow up in when Victor is still on the loose with his creations.
Erika and Jocko have changed the least since the previous books. They've developed a genuine mother-son relationship in the intervening years, and it's heart-warming to see how much they genuinely love and care for each other, especially considering how they both started their lives.
The horror elements of this book did genuinely twist my stomach - the previous army Victor had made were angry and delighted in killing humanity whenever possible, but this iteration of the 'new race' are much less emotional, which makes them much more terrifying. The author did a very good job at revealing the truth of what Victor Clone has made this time - slowly we learn that there are replicants, who are beginning to replace important community figures in the small town the book is set in, in order to make way for the true destroyers of humanity: the Builders.
The Builders are a new invention of Victor's, a mixture of organic and inorganic insects that form together to look like a human, but who are able to latch onto real humans and break them down until there is nothing left. They consume everything that was once a person, and use that organic matter to create more builders.
Having had this truth slowly revealed sent a shiver down my spine - I went into the book expecting something similar to what Victor did in the previous books - created replicants and seeded them throughout the town, killed the real people and hid or destroyed the bodies, but this was so unexpected, and yet such a simple and elegant plan, that it made me feel on edge for the whole book. Every time one of the (human) established characters the story follows entered a new space or met a new person, I was convinced I was about to see them being unravelled into nothing more than cells that would then be absorbed and used to make a new builder. It's like bites in a zombie movie, but somehow worse.
I've definitely read scarier books than this, but for some reason, this really unsettled me and has me looking at everyone around me and questioning if they're about to reach out and unmake me with just a tendril of their weird insect-hive forms.
Definitely one of the best books in the series so far, and I can't wait to get into the fifth and final book!