NEW YORK - In books such as “Slaughterhouse-Five,” “Cat's Cradle” and “Hocus Pocus,” Kurt Vonnegut mixed the bitter and funny with a touch of the profound.

Vonnegut, regarded by many critics as a key influence in shaping 20th-century American literature, died Wednesday at 84. He had suffered brain injuries after a recent fall at his Manhattan home, said his wife, photographer Jill Krementz.

Vonnegut's more than a dozen books, short stories, essays and plays contained elements of social commentary, science fiction and autobiography.

“He was sort of like nobody else,” said fellow author Gore Vidal. “Kurt was never dull.”

A self-described religious skeptic and freethinking humanist, Vonnegut used protagonists such as Billy Pilgrim and Eliot Rosewater as transparent vehicles for his points of view.

He lectured regularly, exhorting audiences to think for themselves and delighting in barbed commentary against the institutions he felt were dehumanizing people.

Some of Vonnegut's books were banned and burned for suspected obscenity. He took on censorship as an active member of the PEN writers' aid group and the American Civil Liberties Union.

The American Humanist Association, which promotes individual freedom, rational thought and scientific skepticism, made him its honorary president.

Vonnegut said the villains in his books were never individuals, but culture, society and history, which he said were making a mess of the planet.

“I like to say that the 51st state is the state of denial,” he told The Associated Press in 2005. “It's as though a huge comet were heading for us and nobody wants to talk about it. We're just about to run out of petroleum and there's nothing to replace it.”

Despite his commercial success, Vonnegut battled depression throughout his life, and in 1984, he attempted suicide with pills and alcohol, joking later about how he botched the job.

Vonnegut was born on Nov. 11, 1922, in Indianapolis, and studied chemistry at Cornell University before joining the Army. His mother killed herself just before he left for Germany during World War II, where he was quickly taken prisoner during the Battle of the Bulge. He was being held in Dresden when Allied bombs firebombed the city.

“The firebombing of Dresden explains absolutely nothing about why I write what I write and am what I am,” Vonnegut wrote in “Fates Worse Than Death,” his 1991 autobiography of sorts.

But he spent 23 years struggling to write about the ordeal, which he survived by huddling with other POWs inside an underground meat locker labeled slaughterhouse-five.

The novel that emerged, in which Pvt. Pilgrim is transported from Dresden by time-traveling aliens, was published at the height of the Vietnam War, and solidified his reputation as an iconoclast.

Critics ignored him at first, then denigrated his deliberately bizarre stories and disjointed plots as haphazardly written science fiction. But his novels became cult classics, especially “Cat's Cradle” in 1963, in which scientists create “ice-nine,” a crystal that turns water solid and destroys the earth.

He retired from novel writing in his later years, but continued to publish short articles.