It's almost unreal how much of an improvement this book was over the last. If I didn't know better, I'd say K.A. stepped in to write this one, but apparently she only wrote the first four. This was certainly one of the more talented ghostwriters the series has had.
After two (!) whole books, we finally return to the ship Mother and find out what happens to Tate, Yago, and the Troika. This story could have been an afterthought but instead it ties in cleverly -- if farfetchedly-- with the main plot while being a strong story in its own right. I connected instantly with Tate: she's pragmatic, brave and thinks outside of the box. She has to struggle for survival from the start, trapped on an empty ship with the people who betrayed her and the other Remnants. But she has one key advantage: the mutation she calls the Mouth.
When Yago tries to feed her to the Troika to accelerate their weird evolution, the Mouth devours him--and here's where things get interesting: instead of dying, his consciousness takes up residence in her head. I could feel shades of Animorphs on the theme of sharing one's head with other minds and fighting them for bodily control. Survival goes in a very different direction though, with the noncorporeal intelligences eventually becoming Tate's companions on the lonely interstellar journey.
Thoughts in no particular order:
1) Survival does amazing character work; not only does it believably develop Tate (whom I wish we'd gotten to spend more time with earlier) but it rehabilitates Yago's character in a way I didn't expect. Not only does he return to the way more interesting conniving Yago from before his brain was scrambled--an effect perhaps attributable to being disembodied?--but by the end he and Tate have lived together for decades and become friends. I was feeling genuine emotions at his death, which I never would have expected.
2) The scale is both intimate and larger in scope. Unlike earlier books, we spend most of the time in Tate's point of view, and this lets us really get to know her and makes the narrative much more immersive. The introspective mode also enhances the existential horror of being possibly the last human in existence, which Tate even weaponizes at one point: they drive Charlie insane by not talking to him, everyone.
Yet the book also effortlessly covers sixty years of Tate exploring the galaxy in a few pages. What could be a jarring time jump is grounded by Tate's quest to find complex life somewhere, anywhere other than Earth. Her failure to do so drives her decision to return, in a moment of narrative resonance I was surprised to get from this series so late in the game.
3) In short, I loved this book. I was very tempted to give it 5 stars, but couldn't justify it in light of how weak preceding books were. You have to read those to understand what's happening here. This is absolutely a 5 star within the context of the series though. It almost makes me sad how much I enjoyed it, because it was like getting a glimpse of how good Remnants *could have been* the whole way through, while knowing that what we got was not this.