I can't recommend Rick Riordan's work enough. After reading all of the novels in the Percy Jackson and the Olympians series and the two books of the Heroes of Olympus series which are available so far, frankly I was a little hesitant to start another series with him. I'd read on Wikipedia that these books are a little darker in tone, and I wasn't sure I was ready for a more serious world than the world of Percy Jackson and his friends. 
 Foiled! My plans to avoid this series were foiled by me 11-year-old son, who brought this book home from the school library, and I'm glad they were. This book was every bit as fun as the Percy Jackson books. It is a little "darker in tone," but the reason isn't that these books are some emo goth manifesto; the Egyptian gods just aren't as wacky as the Greek ones. I'd say Riordan has done a good job of capturing the flavor of the ancient stories in the context of today, making them a little more immediate and accessible to children (and adults). The kids who had him as a history teacher back in his middle school teaching days must have had some amazing class discussions!