William Gass was at the fore of the postmodern literary movement in the 1960s and ’70s. The author of novels such as “Omensetter’s Luck” and “The Tunnel,” he was praised for his ornate and musical prose style. (Michael Lionstar/Penguin Random House)

William H. Gass, whose ornate prose style, experimental novels and labyrinthine essays made him a master of difficult pleasures and one of the most influential writers of American literature's postmodern movement, died Dec. 6 at his home in University City, Mo., near St. Louis. He was 93.

The cause was congestive heart failure, said his wife, Mary Henderson Gass.

Mr. Gass wrote just three novels, none of them bestsellers, but he was often described as one of America's finest literary stylists — "a magician of the word, the writer of a prose so rich that it makes Vladi­mir Nabokov's seem impoverished," Washington Post book critic Michael Dirda wrote in 2013.

Among his most memorable works was a 90-page essay, "On Being Blue: A Philosophical Inquiry" (1975), that plumbed the literal and metaphorical depths of the color blue, and in so doing seemed to mine the very essence of language itself.

"Blue pencils, blue noses, blue movies, laws, blue legs and stockings, the language of birds, bees and flowers as sung by longshoremen, that lead-like look the skin has when affected by cold, contusion, sickness, fear; the rotten rum or gin they call blue ruin and the blue devils of its delirium," Mr. Gass wrote in the book's opening lines, kicking off a list that continued for a page and a half.

Literature was a singular obsession for Mr. Gass, who said that much of his work was fueled by anger, part of it worldly ("I write to indict mankind," he once said) and part of it familial, traced back to a difficult childhood with an alcoholic mother and a father whom he described as a bigot.

Mixing the rigor of a philosopher with the passion of a novitiate, he was a three-time winner of the National Book Critics Circle Award for criticism, for his essay collections "Habitations of the Word" (1984), "Finding a Form" (1996) and "Tests of Time" (2002).

A former student of Max Black, a noted philosopher of language and art, Mr. Gass taught philosophy for decades at Washington University in St. Louis while crafting his essays and fiction, beginning with his 1966 novel "Omensetter's Luck."

Loosely chronicling a man who is wrongly accused of murder in 19th-century Ohio, the book was praised by critics such as Yale University's Richard Gilman, who called it "a whole Olympic broad jump beyond what almost any other American has been writing, the first full replenishment of language we have had for a very long time, the first convincing fusion of speculative thought and hard, accurate sensuality that we have had, it is tempting to say, since Melville."

The novel and its follow-up, the poetically titled 1968 story collection "In the Heart of the Heart of the Country," led Mr. Gass to be labeled as a master of postmodernism. Like his contemporaries John Barth and William Gaddis, he seemed intent on stretching the bounds of contemporary literature, rejecting conventions of plot and narrative pacing.

In place of simple realism, Mr. Gass offered slow-churning stories that were concerned less with mirroring reality than in establishing a whole new world within the text — always messy, and very often dark.

"Historians tend to want to create a narrative, to make the world along the lines of the so-called realistic novels of the 19th century that pretended the world has meaning, that there are heroes and heroines and climaxes and real denouements and turning points," he told the New York Times in 1995, upon the release of his second novel, "The Tunnel." "I happen to believe in none of that, so I feel my book is real realism: there's contradiction and confusion and deliberate darkness."

Mr. Gass's "Tunnel" was a grim 650-page vehicle to another realm, the long-awaited result of nearly three decades' labor. It centered on a Nazi-sympathizing historian who, while putting the finishing touches on his greatest work, "Guilt and Innocence in Hitler's Germany," finds himself moved to write his life story instead. In an unusually dire case of writer's block, he also digs a hole in his basement, the tunnel of the book's title.

The novel drew laudatory reviews from critics who cautioned that it was a difficult, at times painful read. Experimenting with typography, Mr. Gass used the image of a concentration camp tattoo for some page numbers.

While commercial success eluded him, he said that was perfectly fine. In its place he sought an audience of scholars and devoted re-readers — those who devoted time to uncovering and exploring his arcane allusions to Cartesian philosophy or classical music.

"Unfortunately, this book was not written to have readers," he wrote in a letter to the editor of his first novel. "It was written to not have readers, while still deserving them. This is the position I prefer, and I suspect encourages me to my best work."

William Howard Gass was born in Fargo, N.D., on July 30, 1924, and raised in the steel city of Warren, Ohio. His father, a former minor-league baseball player, worked in architecture before being nearly crippled by arthritis.

Mr. Gass burned through the works of Thomas Wolfe in childhood and knew early on her wanted to make a living as a writer, even as he majored in philosophy at Kenyon College in Gambier, Ohio.

"All along one principal motivation behind my writing has been to be other than the person I am," he later told the Paris Review. He went to such lengths as to force himself to create a new handwriting style, as a symbolic break from his childhood self.

After Navy service in World War II interrupted his schooling, he graduated in 1947 from Kenyon and received a doctorate in philosophy from Cornell University in 1954.

He joined Washington University in 1969, and founded the school's International Writers Center in 1990 to host readings by authors such as Lydia Davis and David Foster Wallace, who cited Mr. Gass as a major influence on his work.

A marriage to Mary Pat O'Kelly ended in divorce. Survivors include his wife of 48 years, the former Mary Henderson, an architect in University City; three children from his first marriage, Richard Gass of Cincinnati, Robert Gass of Chicago and Susan Gass of Ann Arbor, Mich.; two daughters from his second marriage, Elizabeth Gass-Boshoven of Kalamazoo, Mich., and Catherine Gass of Chicago; five grandchildren; and two great-grandchildren.

Mr. Gass continued writing until his death, producing essay collections such as "A Temple of Texts" (2006) and the hybrid work "Reading Rilke" (1999), which featured translations and analysis of the German-language poet. He also published a 2013 novel, "Middle C," about a pianist who collects newspaper clippings of murder and atrocity to form an "Inhumanity Museum."

"Try to remember that artists in these catastrophic times, along with the serious scientists, are the only salvation for us, if there is to be any," Mr. Gass told Publishers Weekly in 2015, offering advice to aspiring writers. "Be happy because no one is seeing what you do, no one is listening to you, no one really cares what may be achieved, but sometimes accidents happen and beauty is born."