Mr. Finney specialized in thrillers and works of science fiction. Two of his novels, "The Body Snatchers" and "Good Neighbor Sam" became the basis of popular films, but it was "Time and Again" (1970) that won him a devoted following. The novel, about an advertising artist who travels back to the New York of the 1880's, quickly became a cult favorite, beloved especially by New Yorkers for its rich, painstakingly researched descriptions of life in the city more than a century ago.
Mr. Finney, whose original name was Walter Braden Finney, was born in Milwaukee and attended Knox College in Galesburg, Illinois. After moving to New York and working in the advertising industry, he began writing stories for popular magazines like Collier's, The Saturday Evening Post and McCall's.
His first novel, "Five Against the House" (1954), told the story of five college students who plot to rob a casino in Reno. A year later he published "The Body Snatchers" (later reissued as "Invasion of the Body Snatchers"), a chilling tale of aliens who emerge from pods in the guise of humans whom they have taken over. Many critics interpreted the insidious infiltration by aliens as a cold-war allegory that dramatized America's fear of a takeover by Communists. Mr. Finney maintained that the novel was nothing more than popular entertainment. The 1956 film "Invasion of the Body Snatchers" was remade twice.
Mr. Finney first showed an interest in time travel in the short- story collection "The Third Level," which included stories about a commuter who discovers a train that runs between New York and the year 1894, and a man who rebuilds an old car and finds himself transported back to the 1920's.
He returned to the thriller genre in "Assault on a Queen" (1959) and tried his hand at comedy in "Good Neighbor Sam" (1963), a novel based on his experiences as an adman, played by Jack Lemmon in the film version.
In "The Woodrow Wilson Dime" (1968) Mr. Finney once again explored the possibilities of time travel. The dime of the title allows the novel's hero to enter a parallel world in which he achieves fame by composing the musicals of Oscar Hammerstein and inventing the zipper.
With "Time and Again," Mr. Finney won the kind of critical praise and attention not normally accorded to genre fiction. Thomas Lask, reviewing the novel in The New York Times, described it, suggestively, as "a blend of science fiction, nostalgia, mystery and acid commentary on super-government and its helots." Its hero, Si Morley, is a frustrated advertising artist who jumps at the chance to take part in a secret project that promises to change his life. So it does. He travels back to New York in 1882, moves into the Dakota apartment building on Central Park West and experiences the fabulous ordinariness of a bygone age: its trolleys, horse-drawn carriages, elevated lines, and gaslights. This year Mr. Finney published a sequel to the novel, "From Time to Time."
Mr. Finney also wrote "Marion's Wall" (1973), about a silent-film actress who, in an attempt to revive her film career, enters the body of a shy woman, and "The Night People" (1977). His other fictional works include "The House of Numbers" (1957) and the short-story collection "I Love Galesburg in the Springtime" (1963). He also wrote "Forgotten News: The Crime of the Century and Other Lost Stories" (1983) about sensational events of the 19th century.