4 stars. I'm gonna keep this review short (for the moment at least) : I really enjoyed this book. 
 The world was confusing, the author kept giving us a bunch of informations and I had a lot of troubles to understand everything, replaced the right people to their kingdoms, or who was from where. I also didn't really understand the magic system. It was too much informations in a short times and my brain couldn't keep up. But it didn't keep me from enjoying the plot and what was going on. 
 I like the 4 "main" characters, though I do like Iseult a lot more than the others : I liked her story, I thought she was the most interesting one of them. I do also like Aeduan even though we didn't see him as much as I would have like, I definitely needed more of his pov to understand him a bit more because he is definitely a complex dude. Safi and Merik were alright, I kind of lost interest in them in the middle of the book, I didn't care about them as much as I cared about the other two, and I didn't really care about their romance, it was there it was nice, but meh. 
 Some of the side characters were also really great : Evrane was interesting. I also really liked Kullen and I liked his bond with Merik ((view spoiler)[his death was not necessary in my opinion (hide spoiler)]) 
 Overall, it was a really good first book, I can't wait to get my hand on the second one, as I'm totally on board with that Iseult/Aeduan thing (if it is done right..man, it can be good!)