I agree with everyone reminding us that the book is FICTION.
I also understand why a Christian might be offended. Kudos to any Christian who is well-read enough to effectively shoot down the story.
However, I strongly feel that the Catholic church has brought this on itself. The problem is, Catholics were taught for centuries that Mary Magdalene was a prostitute. (I was taught that in the 70's.) Only recently has the Catholic church admitted it was mistaken. An intelligent person might well ask, if they lied about that, could they be lying about everything else?
To be clear, I doubt that Jesus and Mary Magdalene sired children, but I do think Mary was a close disciple and deserves more credit than she's been given. Recently discovered documents will back my opinion.
Dan Brown saw an opening in the way Mary Magdalene has been portrayed. He has drove a Mack truck through that opening and is now laughing all the way to the bank. It must be hilarious to him that even people like me, who love to remind everyone that it's FICTION, can't resist the arguments for and against his FICTIONAL book.
(I type FICTION in all caps to remind myself that I am arguing that a book, which describes itself as fiction, is indeed FICTION. How silly of me.)