There are some things I like a lot about this book, so two stars seems a bit harsh, but its negative qualities are just so much more prominent and horrible.
So first of all, the sexism in these books is becoming so much more blatant. There are almost no major female characters in the entire series, and I thought finally that problem might be somewhat alleviated with the Quint Trilogy giving us Maris, but no, the authors apparently just shove her offscreen and forget about her for most of the book. They explain this by essentially having the main character do the same thing, which honestly comes off as really unforgivable. Maybe this feels more natural if you're reading them in publication order, but coming into this having just reread Curse Of The Gloamglozer makes it seem like they set up this trilogy with two protagonists and then immediately axed one of them. I ended up kind of hating Quint before I finished the book because of how little he cares about Maris. By the end of it it's clear that she's kind of in love with him (no surprise, since it's a forgone conclusion if you've read the Twig Trilogy first) but throughout most of the book his solo adventures are apparently too exciting for him to even bother to go see her. She writes to him early on to tell him that basically her life is an awful, abusive nightmare, which is something he then does nothing about. Not only that, but it isn't even mentioned again for another 150 pages or so.
Really, the whole plotline with the letters was incredibly upsetting, and not necessarily just in an intentional way. I actually had to skip some of them because they made me want to cry. Maybe this book was not written for abused girls to read. More likely, I think such people's existence was never even thought of. Given the emphasis on the constant death, danger, and treachery of the Edgeworld, I can understand why the authors might have wanted to include some more personal, emotional trauma, but I don't know why they thought it was an appropriate way to keep the only major female character out of the action for most of the book, or why they apparently didn't feel it was important enough to even merit Quint's attention.
I honestly expected to enjoy the romance subplot in this trilogy because, as I said, the Edge Chronicles is all constant sadness and death. Although I loved them as a child and remember them well now, I find myself wondering if I would actually let my children read these books. They're a thrilling adventure, but the constant and horrific violence (which really comes to a crescendo near the end of this book) doesn't seem to be balanced enough. It ends up coming off less as a darker adventure story and more like Game Of Thrones (For Kids!). It can at times feel like the characters live in a world of abject misery and terror. There is some desperate need for a lasting joy and levity for the main characters, which I thought a love story would be the perfect way to provide. While this subplot wasn't necessarily very prominent or well-written in Curse Of The Gloamglozer, it was definitely at least cute. And knowing that in the end the two characters get together (and have a child together) leaves a lot of potential to show us how they got there that never ended up being explored in this book at all. From the Twig Trilogy to here, the question of Maris's existence never seems to be one the authors assume the readers will be interested in.
That was, however, at least one of the things I liked about this book in general: getting to see the backstory of the characters from the Twig Trilogy. The enmity between Quint and Vilnix provides a nice connection to the other books (whatever order you choose to read them in) and the origin of Screedius Tollinix, especially, was a nice touch.
In general, all the greatest qualities of the Edge Chronicles are with worldbuilding. Everything from the maps to the illustrations to the names of characters and the intricate details of the various cultures is both clearly well thought-through and so uniquely weird. The Winter Knights really goes into a lot of detail about the society of Sanctaphrax that the other books haven't, and that's definitely where it shines the most. The Knights Academy can feel a little bit knock-off Hogwarts-y, but there's enough peculiar touches to turn it into something fascinating on its own.
Some of my favourite parts of these books are always the bits where the more fundamental workings of the Edgeworld mythology are revealed, moments like the details of Stormphrax in Stormchaser or the origins of life on the Edge in Midnight Over Sanctaphrax, of which there were a lot in the previous book, so that was something that felt missing through most of this one. But then, in the last twenty pages, out of nowhere we get something completely outside the scope of this story, so that was a pleasant surprise that made the ending really feel satisfying.
All-in-all, this might be my least favourite of the Edge Chronicles books so far, but it does still have at least some of the qualities that make the others so great. If a reader isn't too bothered or upset by the Maris plotline (or lack thereof) and the gory brutality, I think there is something here to enjoy. They just kind of ruined it for me.