As sales of The Da Vinci Code continue to top 100,000 copies a week, according to Nielsen BookScan, a growing list of new and repackaged nonfiction books are playing off or piggybacking on the Doubleday bestseller by Dan Brown. These aren't just existing titles, like Holy Blood, Holy Grail by Richard Leigh et al. or The Gospel of Mary Magdalene by Jean-Yves Leloup, which have become bestsellers in their own right following a one-hour ABC News special in November that explored the novel's controversial theories. The list also encompasses several new hardcover releases that appeal directly to Da Vinci Code readers, and which publishers have had time to sign up and publish as Brown's bestseller maintains its improbably long blaze.

"There's something going on here that's not easily categorizable," said Client Distribution Services' Gilbert Perlman. "You rarely see this [tagalong effect] with a novel."

An Unusual Feedback Loop

CDS is betting that Da Vinci's momentum will keep up through March, when the well-known distributor publishes one of its first books, Secrets of the Code: The Unauthorized Guide to the Secrets Behind The Da Vinci Code, a series of critical essays by journalist Dan Burstein and others. Slated for a first printing of 250,000 copies, the hardcover is the result of an unusual publishing feedback loop. It began when Brown consulted scholarly and religious texts for his novel, which became successful enough to boost sales of those and many related works, and now comes full circle as Burstein summarizes and comments on Brown's sources while explicitly citing The Da Vinci Code. Among the topics addressed are secret societies and the role of women in the church, said Burstein, who described his book as "a kind of Cliffs Notes for people who are thirsty about these topics."

CDS is confident its book can be a widespread hit because of its nonsectarian perspective as well as the original novel's tendency to raise controversial religious questions without full scholarly support. "You finish [The Da Vinci Code] and you just want to know more about all the swirling semi-facts and suppositions," said Perlman, referring to the novel's suggestion that Christ married Mary Magdalene and produced a bloodline that has persisted to the present day. Though Secrets of the Code was originally scheduled for June, CDS moved it up in response to interest from retailers, especially Barnes & Noble.

Appealing to the Faithful

At the other end of the spectrum, religion publisher Thomas Nelson is appealing to readers seeking an informed rebuttal to Brown's book with Breaking The Da Vinci Code. The hardcover, by theologian Darrell Bock, challenges Brown's interpretation of religious history in the novel, including the suggestions that Jesus was married and that the Roman church accepted the divinity of Jesus as a political move.

"So many people were coming up to me or my colleagues and saying, 'My uncle read The Da Vinci Code and now has questions,' or 'You need to publish a book that helps give some solid answers from a Christian point of view,' " explained Nelson publisher Jonathan Merkh. Having found The Da Vinci Code both fascinating and disturbing, Merkh answered the call with this "theologically and historically accurate refutation," which will have a first printing of as many as 100,000 copies. Nelson is packaging it as a kind of workbook, posing questions like "What about Mary, Apostle of the Apostles?" and providing accessible answers, over the span of just 160 pages.

Meanwhile, Touchstone is taking a slightly different approach with a repackaged paperback edition of The Templar Revelation: Secret Guardians of the True Identity of Christ, about the Knights Templar and other secret societies said to know of Jesus' bloodline. The book has sold about 30,000 copies in the year since Brown's book was released last March, compared to 80,000 copies in the previous five years. Now, Touchstone is about to ship 50,000 copies with a new jacket featuring a Renaissance blonde on the cover and a yellow burst that reads: "As Featured in The Da Vinci Code." Gompertz said he has little concern about referencing the novel so prominently, because "it's clear Dan Brown read our book before he published his."

Doubleday Wary, Booksellers Bullish

Doubleday, Random House corporate spokesman Stuart Applebaum acknowledged that when a book is hugely successful, tie-ins are a "publishing fact of life," but that none of them has the endorsement of Doubleday or Dan Brown. "It is very important to the author to us that no potential bookbuyer confuse someone else's Da Vinci-related book with The Da Vinci Code," he said.

Doubleday, of course, is already familiar with other houses capitalizing on Brown's success. Last year, Atria released a new hardcover edition of Brown's previous novel Angels & Demons, along with repackaged paperback editions of that thriller and his second novel, Deception Point, while St. Martin's re-released his first novel, Digital Fortress, all of which went on to became bestsellers.

Although there's a possibility that these new titles from CDS and Nelson could suffer if The Da Vinci Code begins to lose steam, booksellers seem to have confidence in their near-term potential. "I think these books will have some success," said Margaret Maupin, senior buyer at the Tattered Cover in Denver, Colo. "Bookbuyers are interested in the mysteries, but they don't necessarily want another novel—they want the truth, or what someone tells them is the truth."

Publishers also say they're not worried, pointing to the larger renaissance of gnostic books and to the novel's wide and devoted readership. "There are very few decisions we make that seem so without risk," said Touchstone's Gompertz. "This is one of them."