From the introduction:
The Imperial Age: Engines is designed to aid Game Masters who wish to add fantastic machines (known more commonly in the Imperial Age as "engines") in their Imperial Age campaigns. Fantastic engines fired the imaginations of 19th century authors such as Jules Verne and H.G. Wells, and adaptations of their works, especially those that imagine their machines in a retro style, have fired the imaginations of future authors, directors, and roleplayers. An entire subgenre of science fiction, steampunk, has arisen within the last two decades, applying cyberpunk style to the Victorian era.
This supplement gives the GM the tools he needs to design powerful engines of cogs and steam, as well as new advanced classes, skills, and feats suitable for an engines campaign. In addition, a new race, the intelligent automaton, is offered in the appendix.