The Lost Symbol (Doubleday, $25.95) will be released Sept. 15 with a first printing of 5 million copies. That's the largest print run since the 12 million copies of J.K. Rowling's Harry Potter and the Deathly Hallows in 2007.

If Brown's last novel — which has sold more than 80 million copies — "was big, then the new one will be big, big," says Barnes and Noble's Sessalee Hensley, citing "pent-up demand."

She says 50 stores asked for advance copies: "I had to explain there aren't any."

Just the novel's cover, released by the publisher last month, has been enough to trigger Internet debates about the symbolism of images of the U.S. Capitol and the Washington Monument, seen through a keyhole on the book's spine.

Neither the reclusive author, on his relaunched website (danbrown.com), nor his publisher are offering more than cryptic teasers.

"We like to create speculation and intrigue, just the way the books do," says Doubleday's Suzanne Herz, who promises more clues in a "massive" promotional campaign starting Sept. 2.

On his website, Brown says the novel, based on five years of research, is "set deep within the oldest fraternity in history … the enigmatic brotherhood of the Masons" and will explore "the hidden history of our nation's capital."

Most of the nation's founding fathers, including George Washington, were members of the Freemasons.

Brown's editor, Jason Kaufman, says the novel is structured around 12 hours in the life of Da Vinci's Robert Langdon, the Harvard professor and "religious symbolist" played by Tom Hanks in the 2006 movie.

Sony Pictures, which also adapted Brown's 2000 novel Angels Demons last year, owns the rights to the Langdon character. It has yet to sign a new movie deal for The Lost Symbol but is expected to do so.