I read this series many years ago, but, and don’t ask me how, I managed to read the books backward. Yup, I picked up book four. Then book three. Then, despite seriously studying the final (or first) two books, I read book two before reading book one. Because of this, I was easily able to solve the mystery because I remember which characters weren’t in the last (or next) book. But that was years ago and I’ve forgotten so I can read them again and be surprised!