In “Jude Banks, Superhero,” we meet 12-year-old Jude, whose heart has been broken by the sudden death of his younger sister. Irrepressible Katie was brave and impulsive, theatrical and smart. Jude, not quite a year older, was content to live in her shadow, even when people looked right past him to say things about Katie like, “She’s going to take over the world someday, isn’t she?” Jude wasn’t jealous of his sister, he was proud. And then, in one terrible moment, Katie was gone.