I really enjoyed this - while it's a young adult/childrens book, it's also just a good read. There are certainly some things to think about, like the possible choice between saving the world and saving someone you love, but not in a desperate, dark sort of way. I also got the feeling that I was learning a little something about Egyptian mythology, just as The Lightning Thief series contained a lot of info about Greek/Roman mythology.
Fun book to read. I expect I'll be reading the rest of the books in the series as they come along.