The Red Pyramid (Kane Chronicles, by Rick Riordan. Okay, let's be honest, this isn't Percy Jackson. But that's fine, because it's the Kane kids and they have their own problems to deal with. Great introduction to Egyptian mythology and a good story.
Carter and Sadie its the Kane chronicles but I'm puttin it in the Percy j board <<< I just started reading The Red Pyramid yesterday and it's really good! I think Carter and Annabeth would make good friends and Percy and Sadie would make good friends :)