More than 500,000 copies of Brown's thriller were sold in the first week after its paperback release on March 28, Random House Inc.'s Anchor Books said Wednesday. Promotion of the film version, due in May, and reports of the British lawsuit have boosted interest in the novel, said Russell Perreault, director of publicity at Anchor and Vintage books.

''It's really been a perfect storm of events,'' Perreault said. ''There are still a lot of people out there who have been waiting for the paperback to come out.''

Historians Michael Baigent and Richard Leigh are suing Random House, Brown's publisher, for copyright infringement. They claim the author lifted the theory that Jesus Christ married Mary Magdalene and fathered a child from their nonfiction book, The Holy Blood and the Holy Grail, published more than 20 years earlier.

The case, which opened Feb. 27 at London's High Court, drew packed courtrooms for three weeks. It has also sparked a sales revival for Baigent and Leigh's book. Sales of The Holy Blood and the Holy Grail, which graced the New York Times best-seller list in the 1980s, surged 26-fold in Britain and sixfold in the United States during the trial, according to figures provided by Nielsen BookScan and Bookseller magazine, a trade publication.

Random House, which also publishes The Holy Blood and the Holy Grail, denies wrongdoing and argued that Baigent and Leigh's book was itself based on dozens of earlier works.

Baigent and Leigh's plagiarism claim centers on 15 plot points common to both books, including the final resting place of the Holy Grail and the idea that Jesus' royal progeny were guarded by a secret society known as the Priory of Sion, whose ''grand masters'' included Leonardo da Vinci and Isaac Newton.

If they win, the two authors may be entitled to millions in royalties from the novel, which has sold some 40 million copies worldwide, and a ban on further infringement, intellectual property lawyers have said. The case may also clarify to what extent the central ideas of a creative work can be protected in Britain, affecting filmmakers and other artists, lawyers said.

Baigent released a new book last week probing many of the same topics. The Jesus Papers, which suggests that Roman official Pontius Pilate may have staged Jesus' crucifixion before smuggling him safely into Egypt, has sold more than 16,000 copies since March 28, according to Nielsen BookScan.

''These books are a phenomenon right now,'' said Nielsen BookScan's Joel Primer.

Historian Henry Lincoln, who co-wrote The Holy Blood and the Holy Grail with Baigent and Leigh, isn't taking part in the lawsuit.

The film adaptation of The Da Vinci Code, starring Tom Hanks and directed by Ron Howard, is scheduled to open May 19 in Britain after premiering at the Cannes Film Festival in southern France.