Louise Erdrich’s novel “LaRose,” which centers on two Native American families in North Dakota whose lives are upended by a horrific hunting accident that kills a 5-year-old boy, won the National Book Critics Circle Award for fiction on Thursday.

Ms. Erdrich, who has published 15 novels, won in an especially competitive year for high-profile literary fiction, with Michael Chabon, Ann Patchett, Zadie Smith and Adam Haslett among the finalists.

“I’m among such dramatically wonderful novels that it didn’t seem that this was possible,” Ms. Erdrich said in her acceptance speech, before making a passionate plea about the importance of free expression and the need for writers and journalists to challenge falsehoods.

“The truth is being assaulted not only in our country but all over the world,” she said. “More than ever, we have to look into the truth.”

Like virtually every other cultural event these days, the NBCC awards ceremony at the New School on Thursday night frequently veered into pointed political commentary. The ceremony took place not long after President Trump revealed his first federal budget plan, which proposes eliminating the National Endowment for the Arts and the National Endowment for the Humanities, prompting outcries from PEN America and other writers’ groups.

The novelist Yaa Gyasi, whose debut novel, “Homegoing,” won the John Leonard Prize for the best first book in any genre, thanked her parents for the sacrifices they made to bring her family to the United States from Ghana. “In a time where it feels like every day immigrants and refugees are being met with new affronts to their humanity, I am even more grateful,” she said.

In accepting a citation for excellence in reviewing, the book critic Michelle Dean urged her fellow writers not to become complacent about politics or lapse into solipsistic, navel-gazing work that fails to engage with pressing social issues.

“Every day brings a fresh fear, a fresh outrage,” she said. “It’s natural to want to look away.”

The award for nonfiction went to the sociologist Matthew Desmond’s critically acclaimed best seller, “Evicted: Poverty and Profit in the American City,” a deeply reported narrative about impoverished people who lose their homes in Milwaukee, which explores how evictions can be not just a result of extreme poverty, but one of its causes.

The NBCC Awards, which are open to any book published in English in the United States, stand out from other major awards because book critics deliver the verdicts. The finalists and winners, in six categories, are selected by the board of directors of the National Book Critics Circle, which was founded in 1974 and is made up of more than 700 literary critics and editors.

The prize for poetry went to Ishion Hutchinson for “House of Lords and Commons,” which explores the landscape and the author’s memories of his native Jamaica.

The book critic Ruth Franklin won the biography prize for “Shirley Jackson: A Rather Haunted Life,” her study of Ms. Jackson’s life and work. The award for autobiography went to “Lab Girl,” by the scientist Hope Jahren, an American geochemist and geobiologist whose engrossing memoir details her coming of age as a scientist, and her lifelong fascination with plants, trees and soil.

The award for criticism went to Carol Anderson for “White Rage: The Unspoken Truth of Our Racial Divide.” In The New York Times Book Review, Jesse McCarthy said Ms. Anderson’s book “links scenes that should be familiar to us, yet somehow keep falling by the wayside in the story of America we tell.”

The Canadian novelist and environmental activist Margaret Atwood, who was given the organization’s lifetime achievement award, delivered the evening’s most memorable and grim political forecast, as she ticked off the stages societies go through as they slip into totalitarianism.

“Never has American democracy felt so challenged, never have there been so many intents from so many sides of the political spectrum to shout down the voices of others,” she said. “As independent critics, you are part of the barrier standing between authoritarian control and pluralistic, open democracy.”

She expressed gratitude for the lifetime achievement award, but said the recognition was bittersweet.

“Why did I only get one lifetime?” she said. “Where did this lifetime go?”