In an alternate America where the Civil War stretches on, a former Confederate spy turned Pinkerton agent and an escaped slave turned dirigible captain may be pursuing the man -- or are they both being tricked?
This book could have been a lot better with an extra few dozen pages. The characters and setting were interesting (although I was disappointed not to meet again with Briar and Ezekiel from the first volume), but the villains and their Evil Plot were introduced so late and briefly that it was quite anticlimactic, despite some decent gun fights and air battles.
One of the best-done aspects of the world-building was the unusual wealth of sensory details. In too many steampunk novels the technology seems too magical, too clean and easy. Here you get a good sense of the difficulty of wrestling with heavy, unwieldy contraptions while wearing bulky, ill-fitting protective gear, while gunpowder stings your eyes and nose and smoke obscures your vision.