If you've enjoyed the first three books in the Heroes of Olympus series, you should enjoy this one too - unless you're one of those people who gets all worked up because one of the characters comes out as gay - please! But more about that later. I've read all the books in the series so far (as well as the Percy Jackson and the Olympians) because my 10 year old daughter got into them and I tagged along. 
 As an adult reader, I find the writing and character development somewhat lacking, but its good fun and this second series definitely has more depth, and is therefore more enjoyable for an adult, than the first series. So, if you tried the books in the first series and found them lacking, you might enjoy these a bit more - I did. 
 If you like to read the one-star reviews like I do, you will notice that with this book, almost all of the one-star reviews are written by people who are offended that one of the characters in the series comes out as gay - gasp! I am not at all offended that there is a gay character. In fact, I think it's particularly important in pre-teen targeted literature to show that yes, some people are gay, and there's nothing wrong with that. This is a very small part of the plot-line anyway and I doubt this it get much play in the next (and last?) book in the series, but if it does get any, I hope the author will try to reinforce that the gay character was wrong to feel ashamed of his feelings. What does bother me is that the gay character is one that throughout the books, the other characters have thought of as strange, creepy and weird. I don't think that's a great message.