I just finished Dreadnought by Cherie Priest, and while I enjoyed it, I have some sympathy with the person who criticized her making up shit. I have no objection to the explanation of the zombies, since there is no scientific basis for zombies, which are created entirely out of handwavium. However, I can't come up with any way that the Civil War could last 20 years as a shooting war. Two countries with skirmishes on the border, yes, but not 20 years of war. At a minimum, this alternate world had to be one without Antietam and Gettysburg, or there wouldn't be enough warm bodies to carry on, and, as she implies, England would have come into the war on the Southern side. England would have had to pour munitions into the war, because the South was getting short of anything that could be made into bullets. Also, I doubt the cotton economy would have survived the Southern states freeing their slaves in a world where there is still a huge frontier to fill and a Union army for the ex-slaves to join.
Also, she used the word "gentrification."