The initial idea for what has become The Underground Railroad, Colson Whitehead’s much-anticipated sixth novel, pubbing in September from Doubleday, came to him 15 years ago while he was sitting on his couch, letting his mind wander: “In school, hearing about the Underground Railroad, your first thought, at least for a minute, was that it was a literal subway—which made me wonder, what if the Underground Railroad was an actual railroad, literally underneath the earth?”

The Underground Railroad, Whitehead’s eighth book, follows 2014’s The Noble Hustle: Poker, Beef Jerky, and Death, a nonfiction account of his adventures in the 2011 World Series of Poker. Railroad tells the story of Cora, a 16- or 17-year-old slave girl who lives on a cotton plantation in 1850s Georgia. After several brutal public whippings by the plantation’s new owner, she decides to flee north on the Underground Railroad. In the book, Whitehead depicts the Underground Railroad with tunnels, trains, and stations—the better to illustrate the political and social atmosphere of the different American states through which Cora passes.

“On one level, this book is about a girl born into bondage who makes a great leap of faith to escape to a better life,” Whitehead says. “On another level, it’s about slavery, how it functioned and what it meant—to slaves, to their masters, to people in the South. Each state Cora goes through is a different state of American possibility: South Carolina is a benevolent, paternalistic state where slaves are given programs for racial uplift. North Carolina is a white supremacist state. So each is a sort of island, in a Gulliver’s Travels kind of way.”

Why did the book take 15 years to write? Whitehead admits that when he thought up the original concept, he was not in the mood to write it because of the complexity of the subject. Over the years, he says, “I’d take out my notes on this book and maybe add a line or two, but slavery is such a huge subject that I wasn’t ready to go further.” He adds: “But a lot happens to you in 15 years. I got married, I had two kids. Having your child sold off, as happened to many slaves—being a father gave that a deeper dimension for me. Slavery became less of a terrible abstract, as it was when I was a teen and in my 20s, and more of a horrible reality.”

Once Whitehead decided to work seriously on completing The Underground Railroad, there were decisions to be made. “I always try to mix it up with each book—changing tone, changing style keeps the work very vital for me. The Underground Railroad is a very different book from my last one, in which I got the jokes and humor out of my system. Also, I hadn’t written fiction in five years. I considered who the protagonist should be: a teenage boy without a family, fleeing North? A father trying to find his lost son? But I’d already written about fathers and sons. Having had three [books in a row with] male protagonists, I thought it would be good to have a female one. I decided on having a female looking for a mother.”

It flowed freely from there, Whitehead says, with less of the plotting and planning that he usually does. The character of Ajarry, the grandmother whose spirit guides Cora, came easily, as did the narrator’s voice. Then, to acquire a feel for the era and the characters, Whitehead immersed himself in the Slave Narratives, interviews with former slaves recorded in the 1930s as part of the Federal Writers’ Project of the Works Progress Administration (WPA). For Whitehead, these first-person accounts of slavery provided rich illustrations, on multiple levels, of slavery “in the North in the 1790s, in the high cotton states in the 1830s, on big plantations, small plantations, family farms.”

Whitehead is known for taking liberties with his settings, as he does in The Underground Railroad. “While the extent of the human degradation was daunting and I realized I’d have to put Cora through terrible things, I felt free to make four or five different Americas that Cora goes through,” he says. “What could I bring to the paternalistic government of North Carolina versus the relative freedom of Indiana? How can I make North Carolina different from South Carolina, and how were these places different for Cora? Mainly I showed this through the slave patrollers, who were the authority in the 1850s before they had any kind of police force in the South. The patrollers could stop any black person, free or slave, and demand to see their papers. If you didn’t have your papers or an excuse for being off the plantation, you’d be beaten, put in jail, brought back to your master—and that’s analogous to ‘stop and frisk.’ ”

Whitehead’s editor is Bill Thomas, now Doubleday publisher and editor-in-chief. The two have been together since Thomas published John Henry Days in 2001. “It’s rare and a blessing to have the same editor for all these years. He’s supportive, no matter how weird I get!” Whitehead says. All of Whitehead’s novels have been critically acclaimed, and John Henry Days won the Young Lions Fiction Award. Whitehead received a MacArthur Fellowship in 2002 and a Guggenheim in 2013. Before he began writing books, he was a freelance journalist, and since becoming an author he has taught creative writing at Brooklyn College, Columbia University, Hunter College, New York University, and Princeton University, among others.

Now a family man, Whitehead says that it has affected his writing: “Ten years ago when I was working on something, my concern was, should I kill off this character or just give him a flesh wound? Now I’m more protective of my characters. In the past, I didn’t look at my work when the book was done. Now I find myself going back to this book and feeling a sense of accomplishment.”

Once he’s done with promoting The Underground Railroad, Whitehead will mull over his next project, which he suggests might be a novel set in 1960s New York City. Because his books are so different from one to the next, Whitehead says he’s learned not to be presumptuous about who his readers are, because each book brings a different audience: “I once thought my readers were 16-year-old black guys. Then Sag Harbor brought me new readers. Poker players came on for The Noble Hustle. Some people don’t like my fiction, because they prefer the nonfiction. But moving around keeps the work fresh for me, and hopefully for my one or two readers who follow me from book to book!”

At the same time, Whitehead isn’t married to conveying any particular message. “People have asked, ‘What are you trying to say?’ I’m not a teacher, I’m not a historian; I’m trying to create a world for my characters. The pleasure of this book for me is that it’s different from Sag Harbor or The Noble Hustle—but I hope people find it worth their time. And maybe think about American history in a different way. I hadn’t thought about slavery for a long time—so it helped me realize it anew. I hope the reader can take this ride too.”