Thierry Meyssan's book "The Frightening Fraud" is flying off shelves according to booksellers and has topped bestseller lists.
Meyssan, president of Reseau Voltaire, a respected left-wing think tank, reckons the American Airlines Flight 77 that crashed into the Pentagon in Washington, killing 189 on Sept. 11, did not exist and that the whole thing was staged by the government.
"I believe the American government is lying... No plane crashed into the Pentagon," he told France 2 television.
Meyssan did not provide an alternative theory for what may have damaged the Pentagon.
And although French media has scoffed at Meyssan's musings, comparing them to the Roswell alien cover-up theory dramatized in the hit TV show "The X-Files," the public seems intrigued.
"Copies have been flying off shelves," a saleswoman at FNAC bookshop in central Paris told Reuters. It shot to the top of Amazon France's bestseller list and made it to second place in the booksellers' weekly Livres Hebdo's sales list.
Daily newspaper Liberation slammed the book as "a tissue of wild allegations," marveling at its quick rise to fame, from Internet chat rooms, via television chat shows, to bestseller.
Conspiracy theories like the rumors that swirled around the 1963 shooting of U.S. President John F. Kennedy, or the idea that man never actually set foot on the moon, are not uncommon in the United States, but are fairly rare in France.
"This phenomenon is not typical of the French," sociologist Pierre Lagrange told Liberation.
"But the events of Sept. 11 gave us a reality so similar to science fiction, that there has been more of a market for paranoid interpretations."
Meyssan says key evidence shows witness accounts are contradictory, that there are few photographs of the crash and that those that do exist show no debris from the plane.
He also asks why the facade of the Pentagon did not immediately collapse from the shock of the impact and questions the fate of the passengers on the flight.
"What became of the passengers of American Airlines Flight 77? Are they dead?" he asks.
Daily newspaper Le Monde and Liberation both probed Meyssan's theory, tracking down relatives of the victims, and quizzing officials over the crash.
News weekly Le Nouvel Observateur denounced the book as revisionism. "This theory suits everyone - there are no Islamic extremists...everyone is happy. It eliminates reality."
But while Le Monde dismissed Meyssan's theory as flimsy, it admitted that information available did not quite add up.
"There is no official account of the crash...the lack of information is feeding the rumor."
By Rebecca Harrison