An, unfortunately, disappointing end to this series. The final battle doesn't start until roughly 400 pages into this 500 page book (a reflection of the poor pacing of most of the series), only one character that the reader is familiar with dies (shows how there are far less stakes and consequences in this series than in the previous), and the end lacks any kind of finality. 

Honestly, unless you truly love the new characters or you're dying to read The Trials of Apollo, I'd say to just stick to the Percy Jackson series.