Daniel Joseph Boorstin, 89, the prizewinning and bestselling author and historian who had served as librarian of Congress and director of the Smithsonian Institution's National Museum of History and Technology, died of pneumonia yesterday at Sibley Memorial Hospital.

Boorstin was author of two dozen books, which were translated into at least 30 languages. Millions of copies have been sold around the world. The best known include a trilogy on American history, a trilogy on world history and a 1962 social and cultural commentary titled "The Image." In this book, Boorstin coined the phrase "pseudo event," which he described as a staged happening with little or no purpose other than to generate publicity. He also postulated that some celebrities were famous chiefly for being famous.

He won the 1974 Pulitzer Prize for his 1973 book "The Democratic Experience," which was the third volume of his trilogy "The Americans." The first volume, "The Colonial Experience," won the Bancroft Award in 1959, and the second, "The National Experience," won the Francis Parkman Prize in 1966.

"I'm an amateur historian," Boorstin once said. "One of the advantages of being an amateur is that you don't get trained in the ruts, so it doesn't take any originality to stay out of them. I write about what interests me, like packaging, for instance, or broadcasting."

In the course of a writing career that spanned more than 50 years, Boorstin also covered subjects ranging from the evolution of clocks to the first use of elevators and the impact of mail order catalogues. He once described books as humanity's "single greatest technical advance."

He said good history also should be good literature. He was known for an ability to synthesize and for writing, with an eloquence that many professional historians lack, about how strands of history came together.

He taught at the University of Chicago for 25 years, but he never identified with academic historians. He had been criticized for oversimplification and overlooking the more complicated moments of American history, from McCarthyism to Vietnam, and for overlooking the more complicated movements of American scholarship, from multiculturalism to feminist studies.

"He prides himself on not paying a lot of attention to the trends of historiography, but this is history which is also very illuminating," Columbia University history professor Eric Foner told the Associated Press in 1998.

Boorstin was born in Atlanta and grew up in Tulsa. He entered Harvard University at the age of 15, and he wrote his senior honors thesis there on Edward Gibbon's "Decline and Fall of the Roman Empire." Gibbon, he would say later, became a model for his work as a writer of history.

He attended Oxford University's Balliol College as a Rhodes scholar, then returned to the United States, where he received a doctorate in law at Yale Law School. He was teaching at Harvard Law School in 1940 when he met his future wife, Ruth Frankel, who was the sister of a legal assistant working for him.

They met on Christmas. "When he came through the door, I knew this was it. This was the man I was going to marry," she said yesterday. They were married in April 1941, and she would become one of his primary editors over the course of his career.

"Without her, I think my works would have been twice as long and half as readable," Boorstin was quoted as saying in the introduction to "The Daniel J. Boorstin Reader" in 1995.

"He was a joy to edit, and he welcomed it," Ruth Boorstin said. "He welcomed suggestions, and he followed them."

For a period in the 1930s, Boorstin was a member of the Communist Party. This was an act of youthful folly, he told members of the House Un-American Activities Committee in 1953, and he gave them the names of fellow party members.

In 1969, Boorstin came to Washington from Chicago as director of the Smithsonian's Museum of History and Technology, now the National Museum of American History.

He became librarian of Congress in 1975 over the opposition of the Congressional Black Caucus, which opposed his stands against affirmative action and attacks on student radicals during the 1960s. As librarian, he directed a $200 million-a-year operation and a staff of 5,800 in three buildings that held 20 million books and millions more maps, motion pictures, photographs, prints, recordings, videocassettes, presidential papers and such treasures as rare manuscripts and a Stradivarius violin.

He wanted to make the library a "serious but not solemn place," and he ordered the installation of picnic tables around a plaza and instituted midday concerts. Over some objections, he ordered the bronze doors of the Jefferson Building opened, declaring, "They said it would make a draft, and I say that's just what we needed."

In 1987, he retired from the library. "Always leave before they ask you to," he told a nephew, Robert Boorstin, in explaining his decision.

Since moving here, Boorstin had lived in Cleveland Park, in a large and spacious old house where almost all the walls were lined with built-in bookshelves, the way walls in other houses are lined with wallpaper, pictures or paint. He was known for his trademark, hand-tied bow ties, a trait he shared with other Harvard men of his generation, including former Watergate special prosecutor Archibald Cox, former attorney general Edward Levi and presidential scholar Arthur M. Schlesinger Jr.

During his years at the library, Boorstin habitually rose at 4:30 or 5 a.m., went downstairs to his study and wrote on a manual typewriter for two or three hours before breakfast, then went off to work. He continued to write in retirement, including "The Seekers," which was published in 1998. That was the third volume in his world history trilogy, the other two being "The Discoverers," in 1983, and "The Creators," in 1992.

In addition to his wife, of Washington, survivors include three sons, Paul and Jonathan, both of Los Angeles, and David, of New York; and six grandchildren.

Daniel J. Boorstin in the library of his home, where he wrote many books on the shelves.Daniel J. Boorstin won the Pulitzer Prize for the final book in his "Americans" trilogy between posts at the National Museum of History and Technology and the Library of Congress.