Rick Riordan is a very famous YA writer who has written two series about modern teenagers with one mortal parent and one parent who happens to be a Greek god. (It happens.) They go on adventures, save the world, train at their godly summer camps (they exist), and blow up ancient monsters. This has been the general and very enjoyable gist of all of Riordan's YA books up until "The House of Hades." This newest installment in "The Heroes of Olympus" series is told from the perspective of 7 demigods on a quest to stop the evil goddess Gaia from taking over the world and to save two of their friends from dying in the Greek hell of Tartarus. It was a very action-packed story, of course, but it was different from its predecessors in that it had more of a conscience. For example, the two heroes who were banished to Tartarus, Percy and Annabeth, are at one point forced to fight a mob of demons who force them to feel the curses of every enemy and person whom ...