"The Fiend With Twenty Faces" by Edogawa Rampo

Rampo's semi-insane boy's adventure novel. A master villain matches wit and skills with the greatest detective and his young assistant who is 10 years old.  Tokyo of the 30's is the landscape which can be compared to Fantomas' Paris.  The world is about to end or be changed, and Rampo dances on the grave of Tokyo.  Essential young adult literature.