With time running out, the seven demigods must race to complete their quest before Mother Earth rises again. Can they convince Greeks and Romans to work together, or will their enmity continue?

This was a fitting ending to the series. It ties everything off nicely and gives each character an appropriate stepping off point, but at the same time leaves the world open for more to come. Indeed, it quite nicely tees up the next series without committing to anything!

It makes me very happy that these seven demigods have worked themselves into a proper cohesive unit, and their allies outside of the seven all just fall in to the group when they're around. They can all make fun of one another without it being mean, there's no bitchiness or backstabbing, and even if there is jealousy or a dark spot, the characters recognise that it's a flaw in them, not the person they are jealous of. I like the fact that it illustrates that people can have different ways of thinking and approaches to things, and even disagree, but that doesn't mean their friendship isn't as strong or worthwhile as it should be.

I have to say that Leo really stood out for me in this book as a character - it feels like this book is truly his chance to shine. I love the fact that he stands out from the others in the group of seven; IMO he's probably the only one who acts his age! But especially in this story that makes him incredibly endearing, and his decisions even more affecting. 

However, Nico will always be my favourite after reading this series. His character has such depth and I completely love his development. I love the direction the author has taken him in, and I can't wait to read the book that came out earlier this year about him! 

If I have a criticism, it's probably that there are a few too many sub-plots going on. It almost feels like the script to a video game rather than a book. You have the main quest on the Argo II, and then the returning of Athena to Half-Blood Hill. But then there are side quests, bonus levels and of course various bosses to defeat before you get to the Big Bad. It makes for a wonderfully rich and full world, but at the same time trying to keep everything straight can get quite difficult - I feel like I need a save game every so often! 

I'm also slightly disappointed with Octavian. No spoilers, but I was hoping for so much more! 

Overall, I'm very glad I pressed on with this series as it definitely appeals to me more than the original Percy Jackson novels. But now I think it's time to read something other than Greek myth retellings for a little bit. Plus I need to get my hands on the rest of the next series before I dive into part 1of series 3!