Apparently there's a genre for this
There are gods, monsters, ancient prophecies, magical weapons, and children who discover that their parents have been keeping some fairly important information from them. There are quests, battles, secret worlds and, for some reason, a surprising amount of sarcasm. It sounds like fantasy. Easy enough, right? Except that when it comes to Rick Riordan, apparently one genre is never enough. Look at the way his books are described, and the categories begin piling up: fantasy, mythology, adventure, children’s fiction, middle grade, young adult and, occasionally, urban fantasy. Goodreads gives The Lightning Thief several of these labels at once, while professional reviews tend to place it more firmly within children’s or middle-grade fiction. Riordan himself has described the book as a humorous work of fantasy. None of these descriptions are wrong. In fact, they all make sense. But put them together and another question starts to appear: what exactly makes a Rick Riordan book a Rick Riordan...