Dan Brown has become almost as famous as his best-selling thriller The Da Vinci Code, in part thanks to sensational lawsuits and a backlash from some religious groups.

But unlike the mysteries, symbols and controversial theories found between the pages of his novel, the 41-year-old Brown is a relatively open book.

A self-proclaimed Christian, Brown says he enjoys tennis and lists Sarah McLachlan among his favourite musicians on his personal website.

One of his quirks appears to be an affinity for gravity boots. "Hanging upside down seems to help me solve plot challenges by shifting my entire perspective," he says on his site.

Brown begins his day before most -- at 4 a.m. -- which is when he says he feels most productive. An antique hourglass sits on his desk, and each hour he takes a break from writing to do push ups, sit-ups and some quick stretches.

"I find this helps keep the blood (and ideas) flowing."

The son of an award-winning mathematician and professional religious musician, Brown was teaching English at a prestigious prep school in the U.S. when he decided to give up his job and write full-time. That was just 10 years ago.

His interest in code-breaking and covert government agencies led to his first novel, Digital Fortress, which was set within the clandestine National Security Agency. It met with some success, as did his two following novels, Deception Point and Angels & Demons.

However, it wasn't until The Da Vinci Code that Brown garnered the kind of attention that brings both applause and criticism.

In the book, the main character -- a Harvard symbologist by the name of Robert Langdon -- stumbles upon the secret of the Holy Grail and becomes the target of a deadly global conspiracy.

The novel claims Jesus Christ and Mary Magdalene had children, and that the bloodline exists today - a secret covered up by the Catholic Church.

"I worked very hard on this novel, and I certainly expected people would enjoy it, but I never imagined so many people would be enjoying it this much," Brown says on his website.

"I wrote this book essentially as a group of fictional characters exploring ideas that I found personally intriguing. These same themes obviously resonate with a great many people."

Resonate it did. To date, The Da Vinci Code has sold more than 50 million copies, and has been published in 40 languages worldwide. The globe-trotting film adaptation of the novel, directed by Ron Howard and staring Tom Hanks, is set to be released in May.

Brown says he became particularly interested in the mysteries hidden in Da Vinci's paintings while studying art history at the University of Seville in Spain. Years later, while doing research for Angels and Demons, his interest in Da Vinci's paintings was piqued again during a trip to the Louvre Museum in Paris.

"From then on, I was captivated. I spent a year doing research before writing The Da Vinci Code," he says on his website.

But along with Brown's success have come a few thorns. He's had to erect a two-metre-high fence around his home in Rye, New Hampshire, for security reasons. And more recently he has had to fight several lawsuits.

In early April, a British court threw out a copyright infringement suit launched by the authors of the 1982 non-fiction book called The Holy Blood and The Holy Grail.

It was during this trial that it was revealed that Brown's wife, Blythe, was a primary researcher of art and history for his books. She did not attend the trial. At the time, Brown said his wife "dislikes the public attention" and he didn't feel she should have to attend.

A U.S. appeals court also recently upheld a lower court's ruling that Brown did not copy elements of another author's work.

Brown joked about the lawsuits at a writers talk in Portsmouth, New Hampshire on April 23.

"By the way if anybody in the audience would like to sue me, we have forms out back," Brown said to the sold-out crowd. "Just pick one up on your way out."

The author has had his share of religious criticism as well. Opus Dei, a conservative religious group close to the Vatican, says it is unfairly portrayed as a secretive, power-hungry and extreme sect of the Catholic Church in the novel.

Brown's novel places Opus Dei and the Roman Catholic Church at the centre of the cover-up. As well, one of the main characters, an albino named Silas, is a devout follower of the sect.

Opus Dei has asked the studio distributing the film to include a disclaimer saying that they respect Jesus and the Catholic Church. Sony Pictures has not indicated whether it will comply.

As for Brown, he says he is not bothered by the controversy.

"Let the biblical scholars and historians battle it out," he said during the writers talk.

"It's a book about big ideas, you can love them or you can hate them," Brown said. "But we're all talking about them, and that's really the point."

Meanwhile, Brown says he is in no hurry to write a follow-up to The Da Vinci Code. His next book featuring Robert Langdon has no firm release date, although the publishers say it's on the schedule for 2007. It is set within the brotherhood of the Masons.

"I'm in no hurry," Brown said. "I just have to write a great follow up and it'll be done when it's done."