So I picked up this book because it's sequel came up as "Books like Red Queen" and I wanted to read the first book so the second one made sense. And yes you need to read the first to understand the second.
This book has a lot going for it, strong main character and strong female secondary characters. There is next to no girl hate in here and what is there is regulated to a few lines on one part of the book. The only drawback to this is the amount of violent woman death. Thankfully two are dead before the story starts, Seraphina's mother and Lars' mother. Another dies due to being poisoned. While the death of men remains low, one is stabbed, two are beheaded. One before the story.
So what about diversity. We have the county of Porphyry in the north which is known philosophy and technology, these are where the black people are. We get Millie and Abdo from this region. Millie who is a minor character and Abdo a minor to major character.
Don't think we have much in terms of any other representation.
As for the MOGAI front, we have the word "daanite" which comes from Daan and Masha, the martyred gay lovers that were then sainted.
That one thing with the story is that religion runs deep through it. It's made up by reeks a bit of Catholicism. Thankfully there's a glossary in the end of the book.
Overall I enjoyed it, it has it's moments but overall a much better read than Red Queen.