30 books • 3 series
Book #1: Girl Genius
Book #1: Agatha H. and the Airship City
Book #3: Agatha H. and the Voice of the Castle
Book #4: Agatha Heterodyne and the Circus of Dreams
Book #4: Agatha H. and the Siege of Mechanicsburg
Book #1: Girl Genius: The Second Journey of Agatha Heterodyne Volume 1