Do some writers add something controversial to their books just for popularity??

Being controversial helps you to sell copies and make more money. So most authors make use of this tool deliberately to earn more money. Taking in question Dan Brown's books if you take out his controversy about Jesus and Mary Magdalene, I am not sure whether his literal work would be exposed worldwide or not.

They deliberately do that for more popularity. Even though Dan Brown is a great writer he would not have reached the peak in such a short time if not for controversy. I disagree on the part that Davinci Code has nothing special in it. You must read it with open mind to understand why I say so.

Dan Brown did not invent the myth about the marriage of Jesus and the bloodline. I have read the same things in books published before the Da Vinci Code. In his book the myth is told as if it is fact, but it is only meant to be a novel! The history of the Rosslyn Chapel and some religious organizations is based on well known facts, and what he writes about Da Vinci's painting is pure fiction. British writer, Kingsley Amis, one said If you can't annoy somebody, there's little point in writing! He was a man of strong opinions and he knew his books would provoke strong argument amongst the critics. He must have enjoyed reading those reviews which attacked him for his views! He was a very successful author and famous as a controversial and outspoken character. Some writers are deliberately controversial, and others just try to write a good story, then a single aspect of it gets picked up by some critics, and the media makes it into a big story.