The book world has a stimulus plan: a new Dan Brown novel.

Six years after the release of his mega-selling "The Da Vinci Code," the Knopf Doubleday Publishing Group announced that Brown's "The Lost Symbol," a thriller set during a 12-hour period and featuring "Da Vinci Code" symbolist Robert Langdon, will come out in September.

"This novel has been a strange and wonderful journey," Brown said in a statement issued Monday by his publisher. "Weaving five years of research into the story's twelve-hour time frame was an exhilarating challenge. Robert Langdon's life clearly moves a lot faster than mine."

The first printing will be 5 million copies, Knopf Doubleday said, the highest in the publisher's history but well below the opening 10 million-plus print run for the final "Harry Potter" book. "The Da Vinci Code" has sold more than 80 million worldwide and inspired a spin-off community of travel books, diet books, conspiracy books, parodies and religious works.

A film version, starring Tom Hanks, came out in 2006 and made more than $700 million at the box office. Hanks will again be seen as Langdon when the adaptation of Brown's "Angels & Demons" debuts in May.

By Monday night, "The Lost Symbol" was No. 1 on Barnes & Noble.com and approaching the top 100 on Amazon.com. In a sign of likely price wars to come, both sites were offering discounts of 40 percent and higher for the $28.95 novel.

Brown, 44, had kept his readers and the struggling book industry in suspense as year after year passed without a new novel. As far back as 2004, Doubleday had hinted that a follow up was coming, tentatively titled "The Solomon Key" and widely believed to be about Freemasons in Washington, D.C. (Brown has been spotted over the years in Washington, researching Masonic temples.)

Anticipation for "The Solomon Key" was so high that a "guide" to the novel was published in 2005 and remains in print.

Monday's announcement did not say where the story was set or who it would be about, and Doubleday spokeswoman Suzanne Herz declined to offer further information. In "The Da Vinci Code," a murder at the Louvre museum in Paris sets Langdon on an investigation that includes secret religious cults and speculation that Jesus had fathered a child with Mary Magdalene — a scenario that enraged scholars, critics and religious officials, all of it only bringing the book more readers.

Eager for success, but unprepared for obsession, Brown became increasingly reluctant to make public appearances or talk to the media. His reserve was only magnified by a copyright infringement lawsuit that was decided in his favor, but not before Brown was forced to testify in London and prepare an in-depth brief about his career, writing process and the fury he faced when promoting "The Da Vinci Code."

"I recall feeling defenseless because more than a year had passed since I'd researched and written the novel, and the precise names, dates, places and facts had faded somewhat in my memory," Brown wrote.

The trial, too, only made his book sell more.

Inspired in part by the commercial fiction of Sidney Sheldon, Brown is an Amherst College graduate who has said he long gave up on the idea of being a literary writer and instead wanted to write novels read by many. But neither the author nor his publisher nor booksellers expected such a boom for "The Da Vinci Code," his fourth novel, which remained on best-seller lists for more than three years and made million sellers out of such previous books as "Deception Point" and "Angels & Demons."

The long silence after "The Da Vinci Code," far longer than the time spent between his previous books, led to speculation that Brown was hopelessly blocked, as staggered by fame as "Forever Amber" author Kathleen Winsor or Grace Metalious of "Peyton Place," novelists who never again approached the heights of their controversial best-sellers.

Brown is a native of Exeter, N.H., who still lives in his home state with his wife, Blythe Brown, whom the novelist cited during the London trial as a virtual co-author, an energetic researcher who brought an invaluable "female perspective" to a book immersed in "the sacred feminine, goddess worship and the feminine aspect of spiritually."

(AP April 21, 2009)