This is a solid finale to Roirdan's Percy Jackson series. There's lots of fighting and battle sequences, but he manages to keep them fresh and engaging for the most part. I'm a little perturbed that more isn't said about the mortal side of this conflicted. Yes, we're told about all the destruction that's wreaked across the US and in NYC, but what about casualties? That's sort of swept under the rug, which seems strange since Roirdan doesn't shy away from the casualties that the campers suffer.
Anyway, I loved a number of things about this. While it still doesn't have the same depth as the Harry Potter series, there are still a lot of great character. The female characters have their own agency and stories, independent of Percy or any of the male characters, which is not really something I tend to expect when the series is led by a male character given a first person voice.
We're given a lot of background information on Luke's upbringing, and we get to see more of Rachel, Tyson, Grover and Clarisse, who are all given prominent roles to play, though not always in the way we'd expect. I'm especially pleased with the way the love triangle that started to develop in the previous book played out here, since that's not exactly my favorite trope.
This isn't the end of course. There's a new prophecy given at the end of the book for the next series, but even with that, this series can be read on its own.