Wow wow wow, I loved this story. Morally gray characters, a strong female lead, insane twists, a polygamous relationship, and mecha at the Great Wall of China?!?!? Zhao gives us everything in this book. 
I was engaged in this book from start to finish. Zhao does an excellent job of explaining the atmosphere and the magical elements of the story. Their characters are abstract and imperfect, forced to make tough decisions that are shaped deeply by their family and past experiences. The fight scenes with the mecha were profoundly fascinating and exciting, with plenty of detail to help you paint a clear mental picture. 
Overall, this book exceeded my expectations. I cannot believe it's a debut novel. I absolutely recommend it, especially if you are interested in sci-fi,  smashing the patriarchy, and/or mecha anime like Evangelion and Darling in the Franxx.