The main focus if this book is the love story. I was not expecting it and I it's not what I usually look for in a fantasy. It didn't bother me, though, since the romance was well-developed and cute. She always kept him on his toes, and he was disgruntled but impressed by her no-nonsense attitude. I enjoyed that about them.
I also liked the fact that they did not immediately profess to love each other; it's refreshing to see a couple in a YA novel going through the normal stages of "in lust" and "in like" in their relationship, instead of immediately plunging into deep, obsessive love.
The characters were fleshed-out and likable, their motives were plausible. I still don't get the reasons behind the main antagonist's actions, but I'm pretty sure that's supposed to be a mystery and that it will be cleared up in the next books.
The world building was another thing I appreciated. It's not something I have seen before, at least not used like this, and originality is sadly scarce in YA fantasy these days.
What really bothered me were the constant POV shifts, I think that they were unnecessary and they distracted me from the narrative.
The ending also felt too rushed and anticlimactic. The whole book builds up to one single event, and the final showdown was a bit disappointing, at least compared to what I was expecting.
Give "Oath of Servitude" a try if you want a quick, cute read with likable characters and an interesting world-building.