Theodosia and the Staff of Osiris gets my highest recommendation for middle grade and middle school readers. Try it on fans of the Percy Jackson books, kids who are fascinated by Egypt, and anyone who enjoys mysteries with a strong sense of place. But have them read Theodosia and the Serpents of Chaos first - some of the details in this one will make more sense (my review of the first book is here). I know for certain that I would have loved this book as a 10-year-old. I hope that Theodosia has many more adventures.
And, as TadMack pointed out today at Finding Wonderland, this book received "Not one, but two starred reviews, and the School Library Journal invoked the sacred name of Indiana Jones!" Theodosia and the Staff of Osiris is now available for purchase. It would make an excellent holiday gift for adventure fans (perhaps pair it with an Indiana Jones DVD, even)!