I... don't really know what to say. I liked the promised concept, but the execution was tragic.

First off -- I didn't like Nimh. She was dramatic, contradicting, and the corny kind of tragically beautiful-but-hurting YA protagonist. She committed the crime of whispering "run" at the end of a chapter, twice.

North was sometimes bearable. I like that he took actions that spurred on the story rather than just letting things happen to him (which would honestly be understandable given his falling down the sky and everything). I also liked him being introduced as an adventurer/explorer, a trait that was completely ignored as the book progressed.
He is royalty though, which is a big minus point in my book. Monarchies are terrible and boring, especially ones that are as fixated on the bloodline as his. There was also no real meaning to his family ruling over sky island, aside from ~political intrigue~ and ~drama~ because it meant that North couldn't be in a poly relationship with his two friends.

Their romance, though, if that's what you can call it -- urgh bleurgh get it away from me. Insta-love based on nothing, making puppy eyes at each other during moments of terror/danger/death/etc and insane thoughts like "She changed me... When did that happen?"
It can only have happened instantly my man because you've known each other THREE DAYS, during most of which you've been on the run/fighting/hiding.
Or when North says "the way she smiles...". Eugh. My eyes rolled so far back in my head I could see my own brain. At this point they'd spent a number of hours together.
Their every interaction is rushed into stereotypical ~romantic scenes~. Listen, I love stereotype romance scenes, and they can be done well, but all of these were forced and unnatural. I cringed a lot.

Basically, their "romance" is YA dramatic in the worst possible way with no realistic progression whatsoever. North is too much of a horny teenager who loses all critical thought because Nimh is just so tragic and so sad and so beautiful, despite her showing him a number of times she hasn't been trusting him/telling him everything.
It all just feels unnatural and I was completely turned off by whatever chemistry the writers thought these two should be having.

Other grievances of note;
The fight scene with

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Daoman and Elkisa

was clunky and did not read well. What even was going on there...
The Reveal tm that

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Elkisa was actually Insha's lover was so??? huh???? I just didn't understand what on earth it was supposed to add to the story. Except shock value, like oh no... our tragic girl Nimh... She Hath Been Betrayed.... by her own bff.....tragedy....

Nimh basically just believing Insha right away about

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her holding North hostage. based on what??? It's something else to say "this is probably a trap but I'll go anyway because North might be in danger", but no, characters actually using their brain must not be expected to be found in this book.

Nimh just going insane mode???

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When was "killing everyone and everything for Rebirth" on the table?? Hello?????? And then threatening North to make him stay with her magic... Which was then played off as "I'm so sad... I let him go... I loved him too much" what??????????????
And what's worse is that North witnesses this, condemns it, and STILL has the hots for her. Lord.

Before I was even halfway through I just wanted it to be over. I skimmed the last couple of chapters because it was so incredibly freaking boring. The only character I remotely cared about was the bindle cat, because cat. I am sad that his existence only seemed to serve as a thing to facilitate Nimh and North getting closer.

All in all! I had a bad time. I can't even recommend it for fans of YA, that's how flimsy it all was.