Rick Riordan published“Percy Jackson and the Olympians: The Lightning Thief ” in 2005. The book introduces 12-year-old Percy, who discovers that the monsters and demon-eyed teachers who have plagued him his whole life aren’t figments of his imagination: He’s a demigod, it turns out — the child of a human woman and the water god Poseidon — and the Greek myths he grew up learning about are real. To empower his son, Haley, Riordan positioned Percy’s ADHD and dyslexia as strengths: They came from his battle instincts and his innate ability to read ancient Greek.