HBO and the Italian state broadcaster are producing an 8-episode miniseries of the first in Elena Ferrante’s millions-selling Napolitan cycle, “My Brilliant Friend.” They hope to cast two pairs of 8- and 15-year-old girls and all of their friends as from the neighborhood. “The result is an open casting call that has already drawn 5,000 children, the vast majority of whom have never heard of Elena Ferrante, and injected a mix of hysteria and hope into parts of Naples that are poor in resources but rich in real characters.”