The Da Vinci Code is a horrible book. Literarily, the language, descriptions, and puzzles are elementary and uninspiring, often times cliché. The characters are flat, relying on the conspiracy theory to drive the story. And that's where the biggest problem lies.
The first page of the book reads "FACT" and states that descriptions of the secret society, artwork, architecture, documents, and secret rituals central to the conspiracy are accurate. And so the book's first mistake begins even before the story does.
Like all good conspiracies, this story's hinge pin is the Catholic Church and its single-handed involvement in the greatest cover up in human history. The claim comes from two of the main characters--a British Royal Historian and a Harvard symbologist (if two such positions exist)--that the merely human Jesus fathered children with Mary Magdalene and his bloodline exists to this day. When Jesus was deified in a political move by Constantine in the 4th century, the now powerful Church suppressed the facts, demonized Magdalene, and crushed the vibrant worship of her as the sacred feminine due to its threat to the Church's patriarchal structure. All this information, the main character "experts" state, is the true Holy Grail. The text even names actual, seemingly credible books that deal with the subject of the Grail's "true" identity and Christianity's "lost" sacred feminine.
Many of the "facts" claimed on the first page to be accurate are simply false. The claims that the Council of Nicea deified Jesus, who was previously regarded as only a mortal prophet by his followers, and changed the day of worship from Saturday to Sunday to accommodate sun god worship is very poor research of the council. The claim that gnostic non-canonical gospels existed at the same time as and had a following equal to the earliest canonical gospels shows an ignorance of the origin of the Scriptures. Interpretations of Da Vinci's work, most of which contradict interpretations by art historians, are precarious stretches in order to make the story work. And the inaccuracies go on.
The problem of this work of fiction is that it is touted as being “meticulously researched” when it is not. It claims inaccuracies as fact. Couple the inaccuracies with the unfortunate reality that the printed word carries with it an air of credibility, and many readers could believe the claims made in The Da Vinci Code to be gospel truth.
Don't believe everything you read. And don't waste your time reading The Da Vinci Code.