So here they are, the supposed secrets nobody wants you to know, least of all the Christian church. Jesus never died on the cross. No, he retired to Egypt. Or was it France? He sired a royal bloodline with wife Mary Magdalene.
Can this all be true? No, say virtually all serious historians who deal with the first century.
But that doesn't matter in the world of publishing. The staggering success of "The Da Vinci Code" — 40 million hardcover copies in print worldwide plus another 6 million in paperback — has given a boost to books marketed as both nonfiction and fiction that play on the idea that great mysteries envelop the "greatest story ever told."
To people like Lynn Garrett, religion editor of Publishers Weekly for the past decade, the explanation is simple: "Conspiracy theories have tremendous appeal for Americans."
In particular, Brown's novel feeds into "a willingness on peoples' part to believe the worst about Christianity generally and the Roman Catholic Church in particular." She sees it as the religious equivalent of the many theories about President Kennedy's assassination.
Riding in the wake of "Da Vinci" has meant success for books about the Knights Templar, ancient goddess worship, Holy Grail hunts, Vatican intrigue, religious texts that early Christians spurned and the never-ending speculations about the "real" Jesus.
The titles on various best-seller lists lately include "Labyrinth," "The Last Templar," "The Templar Legacy," "The Third Secret" and Brown's earlier novel, "Angels & Demons."
Michael Baigent last week lost a British lawsuit claiming Brown unfairly lifted themes from his co-authored "Holy Blood, Holy Grail." But Baigent can be consoled by brisk sales for his latest conspiracy tome, "The Jesus Papers: Exposing the Greatest Cover-Up in History."
Brown's novel has scholarly characters who purport to present historical facts while Baigent's writings are marketed as nonfiction. But the two rivals agree about religion. Both write that evil churchmen plotted to conceal the truth about Jesus and distort the origins of Christianity, especially the secret that Jesus married Mary Magdalene and was patriarch to a royal bloodline.
Baigent's added twist in his new book has Jesus faking his death on the cross with the collusion of Pontius Pilate, after which he becomes a guru living with the Mrs. in Egypt.
Garrett says "Da Vinci" and company have hit a perfect moment in popular culture, given the actual Catholic cover-ups regarding sexual abuse by priests and the nation's edginess over "the whole specter of terrorism." Another factor helpful to Brown: "A lot of people don't know church history so are more open to whatever is put out there."
Writer Dan Burstein thinks Brown also benefits from current affairs: The Iraq war has made some people more suspicious about official versions of events.
"Conspiracy fits right into that," he said. He also thinks the novel's depiction of the role of women in religion appeals to female book buyers and that the novel comes at "a time of search for new religious answers" as opposed to old ones.
Maybe it's not just modern Americans. Writing in the Boston Globe, author James Parker called Brown's novel "a classic con" and traced conspiracy theories back to 18th-century Europe, where people combined "displaced religiosity" with "ancient longings" a common phenomenon today.
Burstein is completing a documentary based on the 2006 edition of his fan anthology, "Secrets of the Code." That book is among some 30 flooding the market that treat themes in "The Da Vinci Code" itself, another extraordinary phenomenon.
Most are attacks on the novel from mainstream Catholics and Protestants. Because so many people believe Brown's various accusations against the church are "true, or largely true," Burstein says, religious people have been forced to respond. "They see themselves, rightly, as involved in a propaganda war."
Brown has long declined interviews. Baigent denied in a telephone interview that he's a conspiracy theorist.
"I'm in the business of raising questions. I'm not in the business of providing answers. The moment you provide answers, you have a new power structure, so for me it's a journey of exploration," he said. An ex-Catholic, he's suspicious of all belief systems and organized religions. "It's necessary that we question them constantly."
Baigent acknowledged that convincing evidence for his revisionist scenarios about Jesus has yet to appear. He followed leads to several alleged documents that fizzled out.
"I would like to think in due course a lot of this material will be proven," he said, "but it's just a hope of mine."