House of Hades is the fourth, and presumably, the penultimate in Riordan’s Heroes of Olympus series. It continues the story of the seven demigods who are prophesied to work together to prevent the earth goddess Gaea from rising and populating the earth with her giants, presumably a VERY BAD THING. The overall impression I had was that House of Hades was Mark of Athena part II. It follows on directly from and continues the plot points from the previous book. In it the demigods continue to work on the task assigned to them in MoA – to close the Doors of Death. Books one and two form a pair – Jason and Percy’s swap – and so books three and four as well. Riordan has cleared the decks so to speak for the final push in book five, Blood of Olympus. I also had the strong feeling that this is Riordan preparing to say goodbye to the world of Percy Jackson. As far as I understand, his next project is a new series based on Norse mythology (Yeah! Loki! Odin! Thor! Sign me up for that!). Annabeth and Percy’s trip through Tartarus is pretty much a Percy and Annabeth’s Greatest…