Felt like the main plot (with Nikolai and Zoya) was treading some of the same water from the first trilogy, while Nina and Izaak's were doing something new and refreshing. Wishing they had been strong enough to hold up on their own, but no, they're relegated to the B plots. The fantastical elements also become a much larger part of the story, and it stood out from the rest of the series in a way I didn't love.
But as usual with Bardugo, I adored all the characters and will still follow them through to the end of any plot they're given