Rule of wolves is the second book in a duology.However, these books take place in the same world and time as the Grishaverse books. Because of this, I recommend reading the books in this order:1. Shadow and Bone;2. Siege and Storm;3. Ruin and Rising;4. Six of Crows;5. Crooked Kingdom;6. King of Scars;7. Rule of Wolves
Kaz has a small role in Rule of Wolves. When Nikolai and Zoya come to the Crow club, he uses a disguise to eavesdrop. In the end, he helps them escape through the canals mostly because they need him as he needed them once.
She is born a female and is referred to with female pronouns. However, she has stated feeling comfortable in a male body while she was tailored to look like prince Rasmus. In any case, it isn’t clear if Hanne indeed is trans or identifies as non-binary or gender non-conforming.