PARIS — Michel Onfray, a best-selling French pop philosopher, was sounding pretty upbeat on the phone, even though the title of his latest book is “Decadence: The Life and Death of the Judeo-Christian Tradition.”

His book had just come out, with an impressive press run of 120,000 copies, and was selling briskly in spite of — or perhaps because of — its gloomy prognostication. “If you think today about terrorism, the rise of populism, it was important to put that in perspective,” Mr. Onfray said recently. His research, he added, “shows a civilization that had been strong, that had ceased to be so and that’s heading toward its end.”

Mr. Onfray is one of the latest popular authors to join France’s booming decline industry, a spate of books and articles (with a handful of TV shows) that explore the country’s (and the West’s) failings and France’s obsession with those failings. (Last year, the word “déclinisme,” or “declinism,” entered France’s Larousse dictionary.) It’s a phenomenon that cuts across the political spectrum and has picked up velocity in recent years by tapping into an anxious national mood. And its loudest voices are intellectuals with platforms in the national news media.

Beyond Mr. Onfray’s, other books with decline on their minds have appeared in the past few weeks. “The Returned,” a best seller by the journalist David Thomson, is an investigative report about French jihadists who’ve returned home from Syria. “A Submissive France: Voices of Defiance” compiles interviews on France’s troubled banlieues, or suburbs, overseen by the historian Georges Bensoussan. “Chronicles of French Denial,” by the right-leaning economist and historian Nicolas Baverez, is about how France continued its economic decline under President François Hollande.