In the second half of the 19th century, a network of anti-slavery ativists helped slaves from the Southern States of the US escape and flee to the Northern States where slavery had already been abolished, making these states a safe haven for escapees. The trip from the South to the North was long and not one helper or group of helpers accompanied their customers all the way into safety, but a hole network of helpers passed their clients on from one station to the next.

The 19th century was the century of the railroads, and so this network was dubbed the "Underground Railroad". In Whitead's novel, the railroad is quite literally a railroad from steel, operated by engineers and station managers, and with stations that sport real platforms. This is disturbing, because apart from this, setting and plot are realistic. It is sort of an inverted V-Effekt as proposed by Brecht: Because the railroad scenario appears realisti, but we know it to be fiction, we tend to mistrust the rest of the plot which whe think is realistic. Is it really? And what to make of this uncertainty?
I don't know, and maybe there is no answer apart from: Re-thinking and questioning what we believe to be true is always a good idea. And the novel is certainly a good and therefore recommended read.