The House of Hades (Heroes of Olympus #4) by Rick Riordan
Okay, so it looks like the climax of this series will happen in Greece, not that that's terribly surprising. They've been to Rome and are done there, so they're going to go south (possibly following the Via Appia?) hop across the Ionian Sea, rescue Percy and Annabeth, close the surface side of the Doors of Death, and then what?
I really hope that Riordan has enough plot to fill those two books and he can keep the momentum from the end of "The Mark of Athena" going.
Notice that I am not fretting about whether Percy and Annabeth will survive the fall and whether they'll get stuck in Tartarus. Someone will probably have to stay in Tartarus or will die while rescuing them (or both), but I am nearly certain that Percy and Annabeth will survive the fall and emerge alive.
Well, I was wrong about one thing that I can tell you right off. The five remaining members of the Seven and Nico head north, for some unknown reason, which adds all kinds of stops to their trip. They seem to be seeking some kind of pass through the Appenines, rather than having to go around them. I'm not sure why they chose that route. I had a history teacher in college that I disagreed with about most things, but one of the few I agreed with was that in the ancient world, the sea wasn't a barrier, it was a highway. The kids should have used that highway.
And, not unexpectedly, their plan doesn't work out so well, since rather than catching a shortcut, they end up being attacked by the god of each mountain that they pass. While they are trying to find their way through the mountains, Hazel has a conversation with Hecate, who tells her that she inherited a talent for manipulating the Mist from her mother, who, it turns out, did have genuine magical abilities. As the goddess of crossroads, Hecate lays out the choices before Hazel and Hazel chooses the only one in which there is a chance of Percy and Annabeth surviving.
Not surprisingly, the only choice that gives Percy and Annabeth a chance to survive will be the most difficult for the rest of the Seven. Hecate tells Hazel that they have to head north, going through Bologna, and then to Venice. From Venice, they are to take to the Adriatic Sea and sail south towards Greece. Once they reach the House of Hades, Hazel will have to use her talent with the Mist to ensure that they complete their quest.
In each city they are given clues or objects that will make their task at the House of Hades easier, though they will not guarantee their success. Along the way, they, as always, encounter monsters and meet a number of mythological characters -- both gods and mortals.
The travelogue portion of the book includes, as mentioned above, Bologna and Venice. We also see Split, Croatia; somewhere on the northern coast of Africa (at this point, Leo is taking a side trip of his own); Malta; and, of course, the site of ancient Epirus, the modern town of Mesopotamos in Greece.
We also get a travelogue of sorts in the Tartarus subplot. Tartarus is not just a place; it is also a deity, and the trip through Tartarus is actually a trip along (or possibly within) the body of Tartarus. The ground is a membrane similar to skin and the rebirth of the monsters that are killed in the living world involves the monsters being formed within blisters on that membrane. Percy and Annabeth discover that they can drink the Plegethon, which is a river of fire that exists only to keep the monsters alive so that they can be tortured. Needless to say, the Plegethon keeps Annabeth and Percy alive, but doesn't do them a whole lot of good otherwise.
At several points through the book, some of the things that Percy has had to do to make it through his own quests come back to haunt him. In the "Demigod Files" book, Percy, Nico, and Thalia fight the Titan Iapetus. Percy douses Iapetus in the Lethe, which makes Iapetus lose his memory. Percy tells Iapetus that his name is Bob and that he and Percy are friends. Persephone promises to take care of Bob. This, among other things, come home to roost for Percy while he is in Tartarus.
Along the way, we make an important discovery about the motivations of Nico that may well send me back to "The Titan's Curse" to reread all the way through with this new understanding of Nico's motivations.
The characters come to some conclusions about the three remaining lines of the new Great Prophecy: To storm or fire, the world must fall. An oath to keep with a final breath, And foes bear arms to the Doors of Death. Are the kids right about their interpretations of the lines? We find out in one case, but the other two are still undetermined.
It is fairly obvious that Riordan worked up until (and possibly beyond) his deadline on this He did a great job; the book keeps the momentum that Riordan found at the end of "The Mark of Athena" and builds on it. However, there are a few things that Riordan and his editor missed. Just the things that I noticed include the word "off" in a place where "of" would make sense, a missing "the" and one reference to "Millennial Park" in Chicago (the park is actually called "Millennium Park").