There were a lot of worldbuilding details given, but the setting as a whole just wasn't all that believable to me. In particular, in Chapter 2,

we see children being trained to work in the beast's heart. They are punished very harshly for making very minor mistakes, and several are allowed to die just because they didn't instinctively pick up what to do without being taught. This makes NO sense to me. It's a society with a one-child-per-family rule! Their mothers are right there watching them! You're telling me they're all so on board with societal norms that they'll let their own children die rather than give them basic instruction about how to survive in this environment? No! I don't believe it! Frankly, I think it's stupid. I won't be reading the rest of this.

I really wanted to like this. I thought the system and culture surrounding the beast was fascinating and well thought.  That aspect of the world-building truly fascinated me. I loved the writing and how well the two pov narration worked to build the story.

But reading this book was frustrating and heavy for me. That is pretty much a me thing.  But the highly binary reverse sexism of the matriarchal system really brought me down. It leads to a lot of toxicity in family relations, physical and psychological abuse starting from the very first chapter. And I get that it makes sense relating to the world-building, but it made ut impossible for me to like the main character who is blinded by her own privilige and make sexist and transphobic remarks. It's definitely a me thing.  I need to like the characters to push enjoy reading but that aspect hit too close to home for me to enjoy it.

They are a few plots holes in the second part but I think they may be addressed by book 2. 

All in all a book with amazing creativity and world-building, but which is not suited for me.