It's interesting to dive more into Roman culture this time around, especially when reaidng it in opposition to the Greek stuff from the first series. While Greece is more free spirited, Rome is about order and rules.
On top of the mythology lesson readers get from the story, they can also come to realize why Ancient Rome is considered one of the great civilizations of the world.

As for the story itself, well it's standard Riordan. Plenty of action and character development. Even with so many main characters (we're at 7 now, although only 3 were featured here), he manages to give each one their own distinguishable voice. Enough to keep you wanting more (especially with how it ends)!