Edward Jay Epstein, an iconoclastic author whose deeply researched books challenged conventional wisdom on controversies ranging from whether John F. Kennedy was killed by a lone assassin to whether whistleblower Edward Snowden really was who was a Russian spy, died in Manhattan. He was 88.

The cause was complications from Covid, said his nephew Richard Nessel. He said Mr. Epstein was found dead in his apartment on Tuesday.

A professional skeptic, Mr. Epstein has written more than two dozen nonfiction books, many of which deal with allegations of government conspiracies and corporate failure. Some asked more questions than they answered.

In an unlikely start to a productive career, he made his writing debut in early 1966 when he adapted his master’s thesis at Cornell University into a book entitled Inquest: The Warren Commission and the Establishment of Truth. The New York Times called it “the first book to raise serious questions in the minds of serious people,” reinforcing the conclusions of the presidential panel charged with investigating the assassination of President Kennedy in Dallas on November 22, 1963.

That same day in 1963, Mr. Epstein had borrowed his stepfather’s car and driven from New York City to Cornell’s campus in Ithaca, New York, to try to get back to school after missing seven years earlier had failed.

“The entire campus seemed eerily deserted,” he recalled in his memoir “Assume Nothing: Encounters With Assassins, Spies, Presidents, and Would-be Masters of the Universe” (2023), until he encountered a lone student who informed him of the Kennedys Death.

Thanks to a mentor, political scientist Andrew Hacker, in whose class Mr. Epstein excelled, he was readmitted and encouraged to write his senior thesis on the assassination. This gave him access to every member of the seven-member Warren Commission except for their leader, Chief Justice Earl Warren.

His book cast doubt on the commission’s finding that Kennedy was killed by a lone assassin, basing it largely on what Mr. Epstein viewed as serious flaws in the panel’s investigation. “Inquest” was released a few months before “Rush to Judgment.” Mark Laneanother in a tsunami of books suggesting that the commission was hampered by time constraints, limited resources and access, and Judge Warren’s requirement for unanimity to make its conclusions more credible.

“It was the only master’s thesis that I know of that sold 600,000 copies,” Professor Hacker, who now teaches at Queens College, said in a telephone interview.

A decade after Inquest was published, the House Homicide Committee conducted a far more thorough forensic investigation. The report suggested the possibility of more than one shooter and a possible conspiracy, but concluded unequivocally: “Lee Harvey Oswald fired three shots at President John F. Kennedy. The second and third shots he fired hit the president. The third shot he fired killed the president.”

Mr Epstein accepted the results and acknowledged that they answered the questions he had posed. “Given the methodical and open nature of this investigation, there was no longer any mystery,” he wrote.

His subsequent books included News From Nowhere: Television and the News (1973); “The Rise and Fall of Diamonds” (1982), which revealed the economic impact of the diamond industry in southern Africa; “Deception” (1989), based on his interviews with the former counterintelligence chief of the Central Intelligence Agency James Jesus Angleton; The Assassination Chronicles: Inquest, Counterplot, and Legend (1992); and “The Secret History of Armand Hammer(1996), which detailed the ties between this American businessman and the Soviet government in the 1920s and 1930s.

He also wrote “How America Lost Its Secrets: Edward Snowden, the Man and the Theft” (2017), which detailed how Mr. Snowden, as a young U.S. intelligence official, leaked hundreds of American classified documents to news organizations. He became one of the most hunted fugitives in the world. Mr. Epstein concluded that Mr. Snowden did this Defected to Russia and contact with Russian agents, he was less a heroic whistleblower and more a valued intelligence officer for Moscow.

While most of Mr. Epstein’s books have been praised for their meticulous research, Nicholas Lemann wrote in The New York Times Book Reviewwrote that Snowden’s was “an impressively fluffy and golden brown wobbly soufflé of speculation full of anonymous sources and conjectural language.”

Mr. Epstein’s memoir, “Assume Nothing,” is littered with omitted names (about 650 in the index, many of whom he actually knew). they include Jeffrey Epstein (no relation), the disgraced financier and registered sex offender with whom Mr. Epstein once fooled around.

In his column for The New York Times Magazine, William Safire once described Mr. Epstein as “the leading writer in the gray world of spies and moles.”

He was born Edward Jay Levinson on December 6, 1935 in Brooklyn to Albert and Betty (Opolinsky) Levinson. His mother was an abstract sculptor, his father a fur trade financier who died of a heart attack when Edward was seven. His mother remarried Louis Epstein, an English-born shoe manufacturer who adopted Edward in 1945. He grew up in the Midwood section of Brooklyn, where he attended Midwood High School, and in Rockville Center on Long Island, where he graduated from South Side High School.

At Cornell University, Mr. Epstein was an unpredictable student. After the spring semester of 1956, he was suspended for failing four courses, despite receiving high grades in a course on 19th-century European literature taught by Vladimir Nabokov and an A in Professor Hacker’s course at the U.S. Congress.

When he returned in 1963, Mr. Epstein simultaneously completed his bachelor’s and master’s degrees, both in government. He graduated in 1966.

“He was the most interesting student I ever had,” said Professor Hacker. “He had a kind of fake naivety about him. He would act like he didn’t know anything.”

Mr. Epstein earned his doctorate in 1972 from the Harvard-MIT Joint Center for Urban Studies, where his coursework was supervised by Prof. Daniel Patrick Moynihan, the future U.S. Senator from New York.

For three years, Mr. Epstein taught political science at Harvard, the University of California, Los Angeles and MIT and wrote part-time for The New Yorker. But he decided to return to his hometown to become a full-time author instead of pursuing an academic career.

“Ever since I met Clay Felker, I wanted to be in New York,” said the editor of New York Magazine an interview last year with the online magazine Air Mail. “He knew the whole world.”

Mr. Epstein lived alone in a lavish rental apartment on Manhattan’s Upper East Side. His niece and nephews are his closest survivors.

Under the direction of Professor Hacker at Cornell University, Mr. Epstein began to look beyond the conclusions of the Warren Commission and examine how that panel had reached its verdict on the assassination. He was 29 years old, he recalled in his memoirs, and had never conducted a single in-depth interview.

“I still hadn’t finished college,” he wrote. “I had no experience in journalism. I had never worked for a school newspaper or known a reporter.”

But as Richard Rovere, the New Yorker’s veteran Washington correspondent, wrote in the book’s introduction, “Here we have something that should make scientists proud and journalists jealous and ashamed.” Mr. Epstein’s scientific tools happen to be the same ones Using journalists every day. But the press left it to a single scholar to find out the news.”

Mr. Epstein had an insatiable curiosity and wrote about anything and everything, from the economics of Hollywood to the rape accusation against Dominique Strauss-Kahn, the former head of the International Monetary Fund, by a Manhattan hotel maid in 2011. (Mr. Epstein hinted that it was a political production that was staged to embarrass him. Ultimately, Mr. Strauss-Kahn and the maid settled their lawsuit against him.)

Michael Wolff, another maverick investigative writer, said of Mr. Epstein by phone: “He saw his job as a journalist as a challenge or even a subversion of all conventional wisdom, which he did with a rigor that came from thorough research.” and knowing exactly who to call – because it was part of his job to know everyone.”

He added: “Ed’s politics was the joy of skepticism. Was he right? Strangely, I don’t think he wanted to be right. He was all about asking the questions that others had avoided or not thought of.”