De Villiers has always had a penchant for the gruesome and the decadent. One of his models was Curzio Malaparte, an Italian journalist whose best-known book is “Kaputt,” an eerie firsthand account from behind the German front lines during World War II. Another was Georges Arnaud, the French author of several popular adventure books during the 1950s. “He was a strange guy,” de Villiers said. “He once confessed to me that he started life by murdering his father, his aunt and the maid.” (Arnaud was tried and acquitted for those murders, possibly by a rigged jury.) I couldn’t help wondering whether Georges Simenon, the famously prolific and perverted Belgian crime writer, was also an influence. Simenon is said to have taken as little as 10 days to finish his novels, and he published about 200. He also claimed to have slept with 10,000 women, mostly prostitutes. De Villiers laughed at the comparison. “I knew Simenon a little,” he said, then proceeded to tell a raunchy story he heard from Simenon’s long-suffering wife, involving roadside sex in the snow in Gstaad.

This seemed like a good moment to ask about de Villiers’s own preoccupations. “I’ve had a lot of sex in my life,” he said. “That’s why I have so much trouble with wives. In America they would say I am a ‘womanizer.’ ” He has married four times and has two children, and now has a girlfriend nearly 30 years his junior, an attractive blond woman whom I met briefly at his home. When I suggested that the sex in S.A.S. was unusually hard-core, he replied with a chuckle: “Maybe for an American. Not in France.”

One thing de Villiers does not have is serious literary ambitions. Although he is a great admirer of le Carré, he has never tried to turn espionage into the setting for a complex human drama. He writes the way he speaks, in terse, informative bursts, with a morbid sense of humor. When I asked whether it bothered him that no one took his books seriously, he did not seem at all defensive. “I don’t consider myself a literary man,” he said. “I’m a storyteller. I write fairy tales for adults. And I try to put some substance into it.”

I had no idea what kind of “substance” until a friend urged me to look at “La Liste Hariri,” one of de Villiers’s many books set in and around Lebanon. The book, published in early 2010, concerns the assassination of Rafiq Hariri, the former Lebanese prime minister. I spent years looking into and writing about Hariri’s death, and I was curious to know what de Villiers made of it. I found the descriptions of Beirut and Damascus to be impressively accurate, as were the names of restaurants, the atmosphere of the neighborhoods and the descriptions of some of the security chiefs that I knew from my tenure as The Times’ Beirut bureau chief. But the real surprise came later. “La Liste Hariri” provides detailed information about the elaborate plot, ordered by Syria and carried out by Hezbollah, to kill Hariri. This plot is one of the great mysteries of the Middle East, and I found specific information that no journalists, to my knowledge, knew at the time of the book’s publication, including a complete list of the members of the assassination team and a description of the systematic elimination of potential witnesses by Hezbollah and its Syrian allies. I was even more impressed when I spoke to a former member of the U.N.-backed international tribunal, based in the Netherlands, that investigated Hariri’s death. “When ‘La Liste Hariri’ came out, everyone on the commission was amazed,” the former staff member said. “They were all literally wondering who on the team could have sold de Villiers this information — because it was very clear that someone had showed him the commission’s reports or the original Lebanese intelligence reports.”

When I put the question to de Villiers, a smile of discreet triumph flashed on his face. It turns out that he has been friends for years with one of Lebanon’s top intelligence officers, an austere-looking man who probably knows more about Lebanon’s unsolved murders than anyone else. It was he who handed de Villiers the list of Hariri’s killers. “He worked hard to get it, and he wanted people to know,” de Villiers said. “But he couldn’t trust journalists.” I was one of those he didn’t trust. I have interviewed the same intelligence chief multiple times on the subject of the Hariri killing, but he never told me about the list. De Villiers had also spoken with high-ranking Hezbollah officials, in meetings that he said were brokered by French intelligence. One assumes these men had not read his fiction.

What do the spies themselves say about de Villiers? I conducted my own furtive tour of the French intelligence community and found that de Villiers’s name was a very effective passe-partout, even among people who found the subject mildly embarrassing. Only one of those I spoke with, a former head of the D.G.S.E., said he never provided information to de Villiers. We met in a dim corridor outside his office, where we chatted for a while about other matters before the subject of de Villiers came up. “Ah, yes, Gérard de Villiers, I don’t know him,” he said, chuckling dismissively, as if to suggest that he had not even read the books. Then after a pause, he confessed: “But one must admit that some of his information is very good. And in fact, one sees that it has gotten better and better in the past few novels.”