There's something about this year and the ending of many young adults novel series. First Skulduggery Pleasant and now the Percy Jackson series. Unlike the first saga, which ended on an open note, this pretty much seems to be the final chapter in the series.
The reason I say that is because things just end too neatly in the end. And personally, that's one of my pet peeves. It's nothing major, just that things rarely end that neatly in real life, with everyone having found their purpose, their calling, their true happiness, etc, and when that happens in a book, there's also a sense of cognitive dissonance. Yes, I'm a cynical bastard but again, this is just my opinion.
So in the final version, Percy and his crew finally face off against the Titans and Gaia and shit basically goes down. The book is very...busy is a word I would use to describe it. With the way the pacing skips around, trying to showcase the viewpoints of so many different characters, it makes for a disjointed read at times. Especially since for some of the different POV chapters, they'll go "Oh, I have a secret to tell you" and then SKIP to some other POV with the secret being left in the background. Once or twice is fine. But this seems to happen a lot in the last book and while everything is eventually explained in the end, this gets very old very fast.
In terms of this ending and the end for the previous Saga, I think the previous saga packed a bit more of a punch. There was loss and sacrifice and in general, I felt a lot more strongly for that than I did this. It's not something I can really put my finger on but I think that there were just too many different characters having their own POV in this book at times and I didn't feel that was necessary. It's possible to develop a persons character without having to give them a chapter that revolves around their POV.
Overall, I would still pick up this book just to complete the series but it's probably the weakest in the Heroes of Olympus saga, with the House of Hades being much better than this.