Crooked Kingdom is a sequel to Six of Crows, both of which are set in the Grishaverse. It is the story of how Kaz Brekker and his crew as they try to con Jan Van Eck out of his money before he builds an empire with the deadly substance, parem.
As with the last book, the characters are the standouts. Every member of the cast is fleshed out, and you can understand every decision they make. Jesper, Matthias, and Wylan are the standouts in this book. Each of them continue on their arcs in a natural way that leaves their characters feeling complete. Jesper realizes that many of his problems come from hiding his true self as a grisha. Matthias finally sees the beauty in the grisha. Wylan overcomes his father's influence and sees him for what he is.
The plot has constant twists and turns, but is still easy to follow. As the story progresses, the challenges the group faces continually grow more difficult. The characters have to change their plans multiple times to keep up with the growing influence of their adversaries. This story markets itself as a fun fantasy heist, and it more than succeeds in that. It might not say anything particularly meaningful, but it has a few nice messages sprinkled in there.
My main problem with this book is with Inej. Her arc was more or less completed in the last book, and this book doesn't have much for her to do. There's a brief crisis where she believes Kaz only keeps her around because she's useful, but that's resolved rather quickly. She has a rivalry with a character named Dunyasha, but nothing is done with that either. She beats Inej once, then loses the next time they fight. It doesn't make Inej grow or change. It just exists. It might not have bothered me so much if it wasn't built up as this incredible rivalry. I felt that the book wanted her to remain one of the main characters, but had to make up excuses for her to still be in the spotlight.
However, that one critique is rather small. Overall, Crooked Kingdom is a delightfully fun book. I would recommend it to any Grishaverse fans, fantasy fans, or heist fans.