Most alternate histories reverse just a few big historical events. They show us how bad things would be if the Nazis won World War II or the South won the Civil War. Though Ben H. Winters’ new novel Underground Airlines treads familiar territory in this respect, few alt histories are as complex and horrifying as it is.

Underground Airlines is set in a 2016 where slavery is still legal in part of the United States. In this reality, Abraham Lincoln was assassinated in 1861, and the Civil War never happened. Instead, a compromise was struck. To this day, four Southern states (the “Hard Four”) still keep human beings as property.

The book’s main character, who mostly goes by Victor, is an African-American who works as a “soul-stealer”—basically, he’s a bounty hunter who returns escaped slaves to the Hard Four. He works for the Federal Marshals, and he’s the kind of manipulative, coldly efficient monster that often populates films noir. But as he remembers his own experiences as a slave in the South, he starts to question what he does.

Victor infiltrates and explores the world of the Underground Airlines, which is a successor to the Underground Railroad of the 19th century. Priests, teachers, doctors, and police officers work in secret to bring people out of slavery, and they dream of abolition. But in 2016, the dream of ending slavery in America is further away than ever. Much like Colson Whitehead’s acclaimed new novel The Underground Railroad (in which the Underground Railroad involves an actual train), Winters’ Underground Airlines uses an unusual conceit to dramatize the totalizing, horrifying nature of slavery.

The most fascinating stuff in Underground Airlines is in the details—Winters has clearly thought a lot about what the 150+ years since Lincoln’s assassination would have looked like. The result is a United States that is much more isolated from the global community. Under something called the European Consensus, most countries refuse to do business with a nation that still has slaves. You couldn’t buy a Japanese automobile in the U.S. until 2012, and Victor’s car still has a tape deck (The American market is “just catching up with CDs,” the narrator informs us).

The further you go down the rabbit hole, the weirder it gets. We glimpse alternate versions of Michael Jackson, James Brown, Jesse Owens, and other famous 20th century figures. Blaxploitation movies still existed in the 1970s, but they included slaves. There’s a Norman Rockwell painting from 1954 that dramatizes a very different milestone in American history. We get hints of a different version of the Civil War, which happened in the 20th century and involved different players. We also get a look at the complicated politics of an America that has always had slavery and the kinds of Constitutional issues this brings up.

A big part of what’s fascinating about alternate history is catching a glimpse of “our world today, but different.” Winters exploits the notion of modernity existing side-by-side with slavery for all its worth. The cognitive dissonance of seeing the Internet and cellphones in an America where people are still kept as property is disturbing and horrifying because we like to think of slavery as belonging to a barbaric world we’ve evolved beyond.

Underground Airlines is really another way of talking about how the real-life legacy of slavery continues to affect all of us. Most of the book takes place not in the Hard Four but in the rest of the United States, where Victor hunts down an escaped slave named Jackdaw. We get to see the communities, both black and white, that live on the edge of slavery. We witness how the “peculiar institution” seeps into everything—our real-life nightmares of police brutality and discrimination are even more raw because of the suspicion that any African-American could be an escaped slave. We only venture into the world of 21-century slavery near the book's end, and it’s as industrialized and terrifying as you might expect.

Winters is known for mixing detective fiction with other genres—he made some waves with his post-apocalyptic Last Policeman trilogy. Here, he’s basically telling a hardboiled story in the vein of Dashiell Hammett, B. Traven, or Raymond Chandler, in an alternate universe. His morally compromised protagonist is the perfect counterpart to tarnished heroes like Hammett’s Continental Op. The noir tropes, in which the layers of a terrible secret are peeled back and the same people turn up in different settings, work incredibly well to illuminate the dark corners of Winters’ awful world.

The only problem with blending hardboiled fiction and dystopian alternate history comes toward the end of Underground Airlines, when the film noir tropes and the otherwise elegant world-building finally begin to clash. The requirements of a hardboiled thriller call for things to come together in a particular way, one which feels forced in the context of Underground Airlines. The final section of the book—which includes a horrifying, science-fictional reveal—is also the least satisfying, because Winters isn’t quite able to make his noir influences work for him, rather than vice versa.

That said, Underground Airlines manages some powerful moments in the end that offer unsettling answers to the central problem of the novel: How can we remain human in a world shaped by the buying and selling of other humans? You won’t disembark from Underground Airlines with any definite answers, but you probably will find yourself looking at the real 2016 with new eyes.

The best alternate histories offer new perspectives on the real version of historical events. By that measure, Underground Airlines is a triumph.