The Hierarchy of Angels (en Inglés) - William J Whitley

It's 1887, and skilled workmen are randomly disappearing throughout Europe. Ships at sea are going missing in good weather, and high overhead, there are strange things above the clouds. There is a naval engineer on a secret mission. A college professor with his daughter, on holiday. Throw in some inept Pinkerton men, and an enigmatic British artificer, and a megalomaniacal aristocrat hell-bent on restoring the Holy Roman Empire, and you have the recipe for "The Hierarchy of Angels."