I would give this book 5 stars for the characters but overall it's pretty much a 3.5 read for me.
Since it's intended as a duology, I was expecting an ending with a cliffhanger, but not t h a t. My favorite thing about the book is that it read as two different stories in one book with Nina's chapters having little overlap with Nikolai and Zoya's. Also I'm very glad to have to get to know the characters much better.
Now let's move on to the spoilers. I wish this book had been entirely about Nikolai! His life, his Ravka, his triumvirate, his friends. The Darkling plot made me feel slightly bitter, because KOS was supposed to be about Nikolai. I found it redundant that he is back. Ravka has many enemies, financial hardships. It suffers from the tension of rapidly shifting power dynamics. It doesn't need its old enemies back. Besides, I think this book proved how interesting the politics of Ravka is, how delicate a balance Nikolai has to keep without being boring for a second.
I said I liked having two distinct stories in one book, but also I found Nina's chapters the weakest after Matthias' burial. The main plot twist was too coincidental for me to find it plausible. But the Fjerdans were shown in a new light and that was a good thing.
And as for Zoya, it makes me very happy to see a character who was just a jealous rival in the first book of the Grisha trilogy become such an important, unique character. I can't say she's a character I can relate to, or always find likable but that's not required for me to find her interesting. There's only one thing about Zoya, her story made me realize something: almost all the women in the Grisha universe has suffered. Not as a result of the fantasy setting, but for being a woman. I know that is something that applies to many women in real life too, but also it's something that happens a lot in YA, and gives off the impression that only a character's tragedy and suffering can be interesting.
So I guess I loved this book more for the characters and how much more evolved they were than the plot.
I loved the prevailing theme of death and sadness in these poems and came across some very original metaphors. But it was hard for me to retain my focus and I often found myself re-reading the same lines, so I don't know 3.5 stars maybe.
It was a 2 or maybe 2.5 star read until the last chapters. I guessed the villains of the story right but not their motives and the way it all was connected was nice.
But hating the main character and most of the dialogues and thought processes of the characters don't help. I only liked 2 characters, Ms Carp and Christian.
I might read the following books in the series, but I'm not sure.