“It’s not a scientifically based accusation — it’s an ideologically based one,” said the Rev. Thomas Reese, a senior analyst for Religion News Service who visits the Vatican frequently and has written several highly regarded books about the Roman Catholic hierarchy. “One of the problems is that Catholic bishops have never allowed any kind of research in this area. They don’t want to know how many gay priests there are.” Independent studies put the percentage of gay men among Catholic priests in the United States at 15 percent to 60 percent.

In a telephone interview on Thursday, Martel stressed that the 80 percent isn’t his estimate but that of a former priest at the Vatican whom he quotes by name in the book. But he presents that quotation without sufficient skepticism and, in his own words, writes, “It’s a big majority.”

He says that “In the Closet of the Vatican” is informed by about 1,500 interviews over four years and the contributions of scores of researchers and other assistants. I covered the Vatican for The Times for nearly two years, and the book has a richness of detail that’s persuasive. It’s going to be widely discussed and hotly debated.

It depicts different sexual subcultures, including clandestine meetings between Vatican officials and young heterosexual Muslim men in Rome who work as prostitutes. It names names, and while many belong to Vatican officials and other priests who are dead or whose sexual identities have come under public scrutiny before, Martel also lavishes considerable energy on the suggestion that Francis’ predecessor, Pope Benedict XVI, and other towering figures in the church are gay.

Perhaps the most vivid of the double lives under Martel’s gaze is that of Cardinal Alfonso López Trujillo of Colombia, who died a little over a decade ago. According to the book, he prowled the ranks of seminarians and young priests for men to seduce and routinely hired male prostitutes, sometimes beating them up after sex. All the while he promoted the church’s teaching that all gay men are “objectively disordered” and embraced its ban on priests who are believed to have “deep-seated homosexual tendencies,” whether they act on them or not.

Part of my concern about the book is the timing of its release, which coincides precisely with an unprecedented meeting at the Vatican about sexual abuse in the church. For the first time, the pope has summoned the presidents of every Catholic bishops conference around the world to discuss this topic alone. But the book “is also bound to shift attention away from child abuse and onto gay priests in general, once again falsely conflating in people’s minds homosexuality and pedophilia,” said the Rev. James Martin, a best-selling Jesuit author, in a recent tweet. He’s right.

The book doesn’t equate them, and in fact makes the different, important point that the church’s culture of secrecy — a culture created in part by gay priests’ need to conceal who they are — works against the exposure of molesters who are guilty of crimes.