Leslie Kaufman / New York Times News Service

Beating out an unusually competitive field, Louise Erdrich won the National Book Award for fiction Wednesday night for “The Round House,” a novel about a teenage boy’s effort to investigate an attack on his mother on a North Dakota reservation, and his struggle to come to terms with the violence in their culture.

Erdrich accepted the award in part in her Native American language. She said she wanted to acknowledge “the grace and endurance of native women.”

She added: “This is a book about a huge case of injustice ongoing on reservations. Thank you for giving it a wider audience.”

The book was published by Harper, an imprint of HarperCollins. Erdrich is the author of 14 novels including “Love Medicine,” which was published in 1984.

The competition for the fiction prize was considered particularly tight this year. Unlike recent years, when many little-known authors were nominated, the judges produced a high-profile slate of finalists, including Pulitzer Prize winner Junot Diaz, who was nominated for “This Is How You Lose Her,” and Dave Eggers, nominated for “A Hologram for the King.”

The nonfiction category was every bit as competitive and featured established authors like biographer Robert Caro and the late Pulitzer Prize-winning journalist Anthony Shadid, who wrote for The Washington Post and The New York Times.

It was won by Katherine Boo for “Behind the Beautiful Forevers: Life, Death, and Hope in a Mumbai Undercity.” In her book, Boo tells of the heart-rending struggles of slum dwellers living in the shadow of luxury hotels in India.

“If this prize means anything,” she said in her acceptance speech, “it is that small stories in so-called hidden places matter because they implicate and complicate what we consider to be the larger story, which is the story of people who do have political and economic powers.”

Celebrating its 63rd year, the National Book Awards packed some 670 attendees into the elegant Cipriani on Wall Street.

To be eligible for an award, a book must have been written by a United States citizen. Winners received $10,000 and a bronze statue.