5 stars for the reading experience, 4 stars for the craft, so I'm going with 4.5. It was so much fun-- I forgot how fast-paced and satisfying a good YA novel can be. My only complaints are issues that feel annoyingly fundamental, which is why I can't do a full 5 stars.
My first problem is that I really needed more background on the rivalry here. It felt like as soon as we were introduced to the characters, their dynamic began to thaw, and it was more that they were telling us about their rivalry than actually showing us. I think that made it harder to build up the desired tension in the beginning.
And my other big problem is that this book really needed more worldbuilding. I know, I don't think I've EVER said that. Normally I gloss over the worldbuilding in my fantasy books to get to the meat of the story. But I'm so confused about the history and geography at play here. Where is anything? We're in the 1800s (a way that our world marks time) but there seems to be more advanced technology than what we had in the 1800s, and obviously there's all this mythology that we barely get to learn anything about.
My reviews always lean more critical than positive (sorry) but I will emphasize that I absolutely see the hype here and can't wait to read the sequel. The romance gets much stronger and the writing is beautiful. The pacing is also well done, where we aren't running around all the time but it never drags. This is overall a very well crafted novel, especially for YA where I think authors can get a little intimidated, it just had a couple basic issues that could have been worked out with a bit more thought and attention.