I bought this book because I immensely enjoyed Riordan's "Percy Jackson & the Olympians" series. My fear was that this would just be Percy Jackson only with Egyptian rather than Greek mythology. I need not have worried. Although there are similarities (ancient myths in the modern world, young protagonists discovering unsuspected potential, ancient forces stirring after a long hiatus, etc) the differences are significant. Foremost of course are the different cultures from which these mythologies sprang, reflected in the book by coequal brother sister protagonists. Riordan drops a big hint that both series share the same world although this series can be read without prior knowledge of the Percy Jackson books.
The book is longer than any of the Percy Jackson books. Not only this, it has far more of an international flavor with the action jumping from London to New York to Egypt to Paris to Washington and points west. The characters are also of a more cosmopolitan mix than in the America centric Percy Jackson series.
The plot is as good as any in the Percy Jackson series with twists and turns, non stop action, and marvelous touches of humor.
I only wish there were books like this when I was a kid. Highly recommended.