The discovery of some scrolls in Egypt in 1945 provided a source for what Brown calls "an alternative history."
It's believed that the Nag Hammadi scrolls were originally hidden by a monk in the late 4th century, at the same time the bishop of Alexandria ordered them destroyed.
The writings are sometimes called the Gnostic Gospels. "Gnostic" means knowledge, and the groups who wrote them often claimed special knowledge about Jesus.
One of the 50-odd texts contains a line stating that Mary Magdalene was Jesus' favorite and he often kissed her on the mouth, according to Brown. However, the parchments are so damaged that it's hard to be sure what kind of kiss the document is describing.
The texts also identify Mary Magdalene as the companion of Jesus. Brown believes the term means she was Jesus' wife.
Even outside the Gnostic Gospels there is evidence that in the first centuries after Jesus, Mary Magdalene was treated with great respect by several of the early church leaders who were men.
By the year 200 though, women were systematically excluded from any positions of authority, said Pagels. "Throughout history, our history books have been written by the winners," Brown said.
Brown recognizes his book has touched a nerve by dealing with topics that have been forbidden for centuries.
"These are topics that resonate at a deep, deep spiritual level — really at the core of the human psyche," he said.
"Whether you agree or disagree with the topics — they're on the table, and we're talking about them, and these are topics that for centuries have been taboo."