Dang, I adore this series! Rick Riordan can really write. I am currently working my way through the fourth book in the series, The Battle of the Labyrinth, which I practically had to wrestle out of some poor kid's hands (he had just returned it, actually, and I snagged it out of the book drop immediately). This is one of those series that is just as much fun for kids as for adults. And I get a big kick out of talking about these books with kids - and then hearing what other books they think I should read as well.
Yay, Percy Jackson and the Olympians! Rick Riordan, please hurry up and write the next book in the series. Meanwhile I will continue savoring Book 4 until I have to finish it. Then I may go back and re-read the whole series again. That's how awesome it is.