The basic story is the usual nonsense about the Knights Templar and the Holy Grail. As a mystery novel, it's OK, but I don't see what the fuss is about. But there are whole chapters in which vicious anti-Christian lectures are put into the mouths of the characters. Jesus wasn't divine. He was married to Mary Magdalene. She's the "holy grail" because she had a daughter by Jesus. St. Peter was jealous of Mary Magdalene, so he and the early church lied about her being a prostitute. On and on it goes.
Although I was raised a Roman Catholic (my father's faith), my mother was a Christian but not a Catholic. As an adult, although I most definitely believe in God and the basic tenets of Christianity, I really don't adhere to any organized religion. I also don't take insult easily. So for someone like me to be offended by this book, you have to know it is really vicious.
So I can well understand your desire to get some feedback, judgie55, before spending your hard-earned money on a book that sucks you in and then betrays your trust as you get into the middle of it.
I guess she was right! :o)