I want to start by saying I enjoyed the book. It was hard to like Alessandra or Kallias as there are both selfish, power hungry, privileged individuals. I thought I could get over their flaws as I did with Jude and Carden in The Cruel Prince, but Alessandra’s and Kallias’ flaws and growth (if you can call it that) are superficial at best. Alessandra driven to gain power because the first man she loved groomed her then abandoned her and he father treats her as nothing more than a meal ticket. She lacks empathy for others and does whatever she can to elevate her station. Her reasons for planning to kill the king are even weak as it doesn’t appear to be a pattern of queens being docile and removed from ruling. 
The world-building is lacking and the magic system isn’t really a system. If you want a quick and easy read with a decent amount of tension with just enough detail to make it a historical fantasy, then this is the book for you.