"A giant has gone to his rest," said the Atlanta-based speculative-fiction writer Steven Barnes.
He "was one of the great short-story writers our culture has produced," said the Philadelphia-based sci-fi writer Michael Swanwick.
It "is difficult to grasp, emotionally, that we are no longer sharing the universe with this literary giant, this legend, this magician of story," wrote the local sci-fantasy writer Darrell Schweitzer, former coeditor of Weird Tales, which published some of Mr. Bradbury's first stories. "He has been a constant presence for all my life. . . . There is no more Ray Bradbury. It is as if the sun has gone out. He leaves a very large hole in American literature, which can never be filled."
Many writers and readers of the last three generations would agree. Adulation was all over the social media Wednesday, with Bradbury high on Twitter's "trending topics" list.
Mr. Bradbury was born in Waukegan, Ill., in 1920. His small-town upbringing would repeatedly surface in his work, especially his autobiographical novels Dandelion Wine of 1957 and Farewell Summer of 2006. In Twainlike fashion, many of his tales involve small-town boys out to explore.
His family moved to Los Angeles, where he attended Los Angeles High School. In his late teens, Mr. Bradbury started self-publishing in a sci-fantasy fanzine. He first got paid for a story in 1941. From then on, the short story (he wrote more than 600) would be his métier.
His stories found their way into radio and TV shows, including Suspense, The Twilight Zone, and Alfred Hitchcock Presents. He hosted his own successful TV anthology, The Ray Bradbury Theater, airing from 1985-92, first on HBO and then on USA. (TV and film writer Damon Lindelof wrote: "I remember Ray's weekly trip up the elevator in The Ray Bradbury Theater and always wondered if he actually LIVED in that house filled with endless stacks of books.")
Bradbury stories were adapted into several movies, including It Came From Outer Space (1953), Fahrenheit 451 (1966), Something Wicked This Way Comes (1983), and Ray Bradbury's Chrysalis (2008). Besides 27 novels and collections, he also wrote memoirs, essays, plays, poems, and radio, TV, and film scripts.
With Isaac Asimov, Arthur C. Clarke, and Robert Heinlein, Mr. Bradbury was one of a quartet of postwar writers who personified the golden age of sci-fi, turning out novels, stories, TV shows, and movies that told the present by fantasizing the future.
But Mr. Bradbury "stood apart, very noticeably, from the others," said Mathew Kaplan, producer of the radio show Planetary Radio ( http://bit.ly/IBPEMO) for the Planetary Society. "He was the poet of the genre."
Rock Robertson, former president of the Philadelphia Science Fiction Society and member of the programming board for Philcon, the Philadelphia Conference on Science Fiction and Fantasy, loved Mr. Bradbury's characters: "For all his work describing dead worlds inhabited by alien ghosts, postliterate societies, haunted carnivals, and prophetic animated tattoos, his true strength was characterization. His people leaped off the page and into your imagination, bringing you into the story."
Schweitzer added: "His importance . . . is in humanizing much of science fiction, in showing by example that it was not merely OK but a superior means of storytelling for the [science-fantasy] writer to get in touch with genuine feelings. He did more than anyone else to move science fiction into the literary mainstream."
In his first big success, the 1950 collection The Martian Chronicles, colonizers from Earth destroy a beautiful utopia on Mars. Human prejudice, superpower politics, and soulless capitalism are the culprits.
Those tales are "about his Mars," said Swanwick, "the Mars of old canals and dying races and ancient civilizations and crystal towers. . . . [H]e knew that his Mars didn't exist, that the science had long moved on far beyond that. He wasn't so much interested in the science, but the poetics and the beauty of the story. . . . Nobody did that better than him."
Telling the future
The tales of The Illustrated Man are often apocalyptic warnings; repeatedly, the human mind collides with the machines that mind has wrought. The wandering Man of the title bears animated tattoos created by an artist from the future. The Man himself eludes a fixed meaning.
The Bradbury vision certainly foretold the future. "A Sound of Thunder" anticipated what's now known as the "butterfly effect," in which tiny disturbances in time or space touch off huge consequences far away. His story "The Veldt" takes two boys into a dangerous world that anticipates today's video gaming. In the story "I Sing the Body Electric!" three children weigh the relative merits of human and android grandparents.
In Something Wicked This Way Comes, two boys at a traveling carnival find themselves plunged into a nightmare battle between good and evil. Kaplan recalled how he and his wife read Something Wicked aloud to each other. "We were spellbound," he said. "He wrote like the greatest of impressionist painters painted. The language, the images, the threats, and the joys, so vivid and so beautifully depicted."
Mr. Bradbury was a huge supporter of libraries. He disliked digital books, and saved several libraries from censorship or closure. His hatred of censorship emerged in Fahrenheit 451, an unforgettable myth of totalitarian mind control and the indispensable role of the written word. Fittingly, he wrote the book on rented typewriters at UCLA's Powell Library in little more than a week.
Jacob McMurray, senior curator of the Science Fiction Museum and Hall of Fame in Seattle, said: " Fahrenheit was written as a reaction to the McCarthy era and anticommunist freak-out in America. Mr. Bradbury often used his works to comment on society, though he didn't have any specific political agenda. His works addressed . . . personal freedom and how it is impinged upon."
Those who knew Mr. Bradbury, who is survived by four daughters and eight grandchildren, described a genial, gregarious man. Barnes said, "He was very encouraging to me as a writer; he's the last of the old gods." When Barnes gave a talk onstage with an aged Bradbury, breaking into tears when he spoke of his debt to him, Mr. Bradbury wrote back later that "some of your tears are mine."
("I regard his  book Zen in the Art of Writing as all you need to know if you're a writer," said Barnes. "You're always going to be hurt; you're always going to be scared. Do the work. Write.")
Kaplan, who worked often with "the man I think of as Uncle Ray," said Mr. Bradbury "loved L.A., loved talking to other writers, loved being the center of attention, and most of all, showed up at every conference, meeting, and event, to talk about his work, writing, and all his great stories.
"I'll always be grateful the books will stay with us," Kaplan said, "but today I'm really, really sad to lose a man who was such a delight."
Contact John Timpane at 215-854-4406 or firstname.lastname@example.org, or follow him on Twitter, @jtimpane. Tirdad Derakhshani contributed to this article.