A Union operated, heavy-armored steam engine, the titular Dreadnought, is the centerpiece of this novel. In the world of the Dreadnought, the Civil War has been going on for so long that even much of the South has freed its slaves. Texas remains an independent Republic and Mexico is ruled by Emperor Maximilian.
The protagonist is Mercy Lynch, a nurse working in the Confederate war hospital in Richmond, Virginia. She begins the story doing what a nurse in a war hospital does: dealing with the bloody aftermath of the ongoing war, a job which she continues even learning that her husband (a Union soldier) has died in a POW camp. It's the news that her estranged father is dying and wishes to see her, however, that takes her from her duties and on a collision course with the Dreadnought.
Mercy's father lives on the other side of the continent in Seattle, Washington, which isn't even part of the United States yet. Mercy's journey will take her through the wall-torn South and farther into untamed West.
In comparison to the previous Boneshaker, Dreadnought is rather slow. This is due, in part, to the fact that this is a "journey" story. In fact, for much of the first 200-pages, not a heck of a lot happens. Even the hospital scenes, with their blood and gore, aren't terribly gripping. To the story's credit, once Mercy finally gets on board the Dreadnought, things really start to pick up, but it takes a while to get there.
The biggest weakness is by far Mercy herself. She's competent and certainly brave, but rather humorless and emotionally distant. For example, her reaction to her husband's death is rather flat, too accepting. One might argue that this is function of the times, that a nurse, in particular, has to be tough. But there was something flat about her characterization. It may have been that I really didn't care about her motivation. Namely, her decision to travel clear across the country to see the father who abandoned her as a child. Honestly? I really don't know why she did this. I can't really say I care.
In Boneshaker, OTOH, Briar's motivations are immediately understandable. She wants to save her son. For all her difficulties with their relationship, they have a relationship and she loves him. Mercy, however, seems to be chasing a ghost.