On a whim one day midway through a 2009 research trip to her native Ghana, novelist Yaa Gyasi decided to tour the infamous Cape Coast Castle, a colonial-era fortress along the Ghanian coast where British soldiers housed captured African slaves before loading them onto ships bound for the plantations of the Caribbean and the American South.

“As a writer, I had never really had a moment where I was struck by inspiration before,” Gyasi says of that fateful visit, during a call to the Straight from her home in Oakland, California. “But stepping into that castle, you instantly feel—even if you don’t believe in ghosts, you instantly feel the weight of the fact that so many people died in that place.”

On her tour of the castle, Gyasi, then a student at Stanford University, learned that British soldiers stationed there had married local African women and lived with them in relative luxury while other Africans languished in horrific conditions in the dungeons below. “I immediately had this picture of these two juxtaposed women, the woman who has been the wife of a British officer and the woman who would have been kept in the castle dungeon,” Gyasi recalls.

Over the next six years that image grew into Gyasi’s debut novel, Homegoing, which was bought by an American publishing house for about $1 million and earned Gyasi rapturous reviews from critics when it was published in June.

In the novel’s fablelike opening chapters, two half-sisters, Effia and Esi, end up at the Cape Coast Castle, Effia as the child bride of a British officer, Esi as a slave imprisoned in the dungeon awaiting transport through the notorious “Door of No Return” to a slave ship bound for the Americas. From there, Homegoing traces an epic journey across more than 250 years of often bloody history as it follows Effia’s and Esi’s descendants in Africa and the United States from the mid-18th century up to the present day.

Like her novel, Gyasi (her last name is pronounced “jessie”) is herself at once deeply Ghanian and thoroughly American. Though she was born in Ghana, her family left Africa when she was two so her father could pursue graduate studies at Ohio State University. After that, Gyasi and her family bounced around college towns in the U.S. until her father landed a teaching job at the University of Alabama in Huntsville when Gyasi was 10.

Gyasi, now 27, describes a girlhood divided between her traditional Ghanian family, who instilled in her a rich sense of her African heritage, and a daily life in Alabama where the long shadow of American slavery and segregation coloured her every interaction with friends and schoolmates.

“Alabama has a reputation for a reason,” she says. “If you come from a place like Ghana where you’re not used to having to think about yourself in terms of your race and then end up in a place where you’re daily confronted by your race, it starts to inform the way you identify, and so for me Alabama was the first place I started to think about blackness, about what it meant to be black.”

Gyasi credits her status as perpetual outsider for her ear for dialect, black and white, American and African. But the fact that, as she puts it, she has “never felt Ghanian enough for Ghana or American enough for America” may also account for Homegoing’s singular blend of emotional intimacy and dispassionate historical analysis.

The novel pulls no punches in its depiction of the horrors of slavery and its aftermath, showing not just a brutal whipping and lynching of an enslaved mother and father on an Alabama plantation, but also the fierce battles between the African tribal nations, the Fante and the Asante, who competed to supply European traders with a steady stream of slaves. But one never feels the author’s thumb on the scales of history. James Collins, the Englishman who marries Effia early in the novel, is a decent man, while a number of the African and African-American characters are deeply flawed. Few of Gyasi’s characters are irredeemably good or bad, though they are all in one way or another complicit in one of history’s greatest crimes.

“There’s a castle on the coast in Fanteland called the Cape Coast Castle,” Gyasi has a character explain in the later pages of Homegoing. “That is where they used to keep the slaves before they sent them away to Aburokyire [abroad]: America, Jamaica. Asante traders would bring in their captives. Fante, Ewe, or Ga middlemen would hold them, then sell them to the British or the Dutch or whoever was paying them the most at the time. Everyone was responsible. We all were…we all are.”

Yaa Gyasi will discuss Homegoing on October 20 and 21 at the Vancouver Writers Fest. Go to the Writers Fest website for more.