Until recently, the Man Booker, which was first awarded in 1969, was restricted to novels written by authors from Britain, Ireland and the Commonwealth nations. In 2014, the contest was opened to any novel written in English and published in Britain. Past winners include Margaret Atwood, Kazuo Ishiguro, V .S. Naipaul and Hilary Mantel.

Image Credit... Sonny Figueroa/The New York Times

The expansion of the prize parameters has drawn criticism from some in the literary world, who warned that the Booker would lose its British character with the incursion of American writers. After Mr. Beatty won last year, a group of writers, including Julian Barnes and A. S. Byatt, denounced the decision to let Americans compete. Ron Charles, a book critic for The Washington Post, criticized the list of finalists for being overly American, writing that “for any serious reader of fiction in this country, the Americanization of the Booker Prize is a lost opportunity to learn about great books that haven’t already been widely heralded.”

In addition to Mr. Saunders, the other Americans to make the list of finalists were Paul Auster, who was nominated for “4321,” an epic narrative that tells a Jewish boy’s coming-of-age story in four different versions; and Emily Fridlund, for her debut novel, “History of Wolves,” about a teenage girl growing up in a commune in the Midwest.

The other finalists were the British novelist Fiona Mozley, whose debut novel “Elmet,” centers on a single father raising his teenage children in rural Yorkshire; the British-Pakistani writer Mohsin Hamid, nominated for “Exit West,” a surreal, dystopian story about two refugees fleeing a civil war through magic doors; and the British novelist Ali Smith, whose novel “Autumn,” about the relationship between a middle-aged British woman and an elderly man, explores the rise of British nationalism. Ms. Smith, who has been shortlisted for the Booker four times, was considered a favorite to win this year.

“Lincoln in the Bardo” won near-universal praise from reviewers when it was released in February, and became a No. 1 best seller. In a review in The New York Times, Michiko Kakutani wrote that “Saunders’s extraordinary verbal energy is harnessed, for the most part, in the service of capturing the pathos of everyday life.”

Before he wrote “Lincoln in the Bardo,” Mr. Saunders, 58, was best known for his dark and often funny futuristic, dystopian short stories. Born in Amarillo, Tex., and raised in and near Chicago, Mr. Saunders never imagined growing up that he could one day write for a living. He got a degree in geophysics from the Colorado School of Mines, then worked as a geophysicist in Indonesia, where he read to keep himself occupied at a remote camp. When he returned to the United States, he supported himself with odd jobs, working as a doorman, a roofer, in a convenience store and in a slaughterhouse.

He eventually enrolled in an M.F.A. program at Syracuse University, and in 1996, he published his debut fiction collection, “CivilWarLand in Bad Decline,” which established him as an innovative writer with a dark, demented streak. He went on to publish several other collections and novellas, including his widely celebrated 2013 short story collection, “Tenth of December.”