I picked up the first issue of this limited series because it was free. And it still is free on Kindle, at the least.
I think I first heard about John Henry because of a cartoon short. At any rate, before I saw John Henry the horse, I knew who John Henry was and, therefore, knew who the horse was named after (he lived up to the name).
Harris' reimagining of the story places Henry in a steampunk universe. It is long the lines of the Clockwork Century (though it is different. No zombies for one). The story does tie into the origin John Henry myth and then moves forward while using the myth/legend.
What is particularly enjoyable about this series is the role that Polly, John Henry's wife plays. Some people may not know that Polly had her own set of stories and songs. Harris does, apparently, and what Polly does is great. Her role is great. I really hope that Harris writes a graphic novel about her, and considering the closing panels of this book, a follow up to this book as well.
Harris does address the issues of racism and slavery, not just in terms of John Henry (a Black man) but also in the use of other characters and settings. He confronts the racism that existed (and still does) against the Chinese population whose labor was used to build the railroads.