“Agatha H and the Voice of the Castle” by Phil and Kaja Foglio.
Title: Agatha H and the Airship City
Series: Girl Genius (novel series)
Number in Series: 3 (one)
Author(s): Kaja Foglio, Phil Foglio
Cover Artist: Tom Kidd
Language: English
Publisher: Night Shade Books
Published: November 2014
ISBN-10: 1597802956
ISBN-13: 9781597802956