I admit that I am having a bit more difficulty being swept away by Riordan's Egyptian mythology series. It's probably lack of background knowledge and experience. I've studied and been surrounded by the Greek and Roman gods of his Percy Jackson series since I was in 7th grade. I know little of Egyptian gods.
It would be a good idea to begin reading up on them. I've always been a fan of Elizabeth Peter's Ameila Peabody series set in Egypt. Perhaps I would get more out of them if I understood more of the Egyptian history and gods. Riordan seems to have worked hard to find characteristics and interrelationships between the gods--although I expect much of it has to be creativity on his part.
I'll be interested in how teens respond to this series. So far reviews on the Barnes and Nobel site suggest it is being well received. It does have several advantages as far as characters go. We have both a male and female main character (brother and sister). There is also a secondary character with a fatal genetic condition.
Meanwhile, the next book in the Heroes of Olympus series is due out in October. If I don't get through the research on Egyptian mythology I at least have the next Olympian book to look forward to.