[Mark]

Rick Riordon has written several book series. Several of the series share the same "universe," starting with the "Percy Jackson and the Olympians" series, and revolve around individuals who are demigods (individuals who are the offspring of one of the Greek gods and mortal), in which there's a camp (Camp Half-Blood) set up just for them to be able to live together (they can live there either for the short-term or permanently). The third series, "The Trials of Apollo" follows Apollo (who's narrating the story in the first-person) after he irks off Zeus once too often and gets turned into a mortal teenager. In the first book ("The Hidden Oracle") Apollo makes his way Camp Half-Blood and meets some of his demigod children, one of whom Apollo says he had with a human male (though he never goes into any details as to how that happened).