The chapters are very short - sometimes less than a page, never more than 5 pages - and often cover more than one scene. It's writing for ADD victims (or American TV addicts).
In a nutshell, avoiding spoilers here, there's a murder in the Louvre, and the clues send the plot on a search for the Holy Grail, complete with secret religious sects, Vatican intrigue and Crypro-Symbology Experts in Love. Well, lust, actually.
Part of the cryptology had to do with a Hebrew encryption scheme, and Brown got almost every detail of the technical description wrong. He consistently makes the mistake of putting in Hebrew words with the letter "j". There is no "J" in Hebrew. He also doesn't understand how the Hebrew "V" becomes a vowel (O or U, depending on the placement of a dot), and his explanation shows his ignorance.
He also makes claims about Jews having sex in the Temple as part of their original rituals, when in truth it was pagan practices such as this which Judaism was created to avoid. But it's a book of fiction, and he was inventing that bit to bolster other bits of fiction.
The book was written to be made into a movie. All the characters are unique individuals, from the chief of Paris police, known as The Bull, to the massive albino monk, to the sexy Paris policewoman/cryptographer to the Harvard tweed symbology professor who plays opposite her. It even leaves room for a sequel and prequels galore. Not that anyone would pay money to see them.
I read the book to see what the fuss was about, and the answer is that nobody who actually read the book could ever mistake it for a serious religious tome. All the protests you see are by idiots who have not read the book, who have taken the word of someone else who has not read it, who is knee-jerk reacting to something someone heard on Oprah.
I may rent the DVD of the movie, not to see the whole film but to see how Hollywood handles the murder scene which features a naked elderly man spread-eagled on the floor. And maybe also for the pagan sex ritual scene, but that's only a few seconds of time in the book.