The lists of books of the year are often as instructive for what is left out as for what our assorted literary celebrities choose to include in their pre-Christmas recommendations. We know from their recommendations this year that most of our cultural opinion formers have, on the whole, little or no interest in the bestseller lists and in the books most people are reading. If they do mention a bestselling novel, it is invariably to disparage or ridicule it, as Clive James ridiculed Dan Brown’s concept thriller The Da Vinci Code while bestowing his end-of-term favours in the Sunday Telegraph.

But at least he had taken the trouble to read and mention a novel that was the significant omission from all other books-of-the-year lists. For The Da Vinci Code is surely the book of 2004: bought, read, recommended, loaned and discussed by hundreds of thousands of people in this and many other countries. First published in spring 2003, it is at present the number one bestselling novel in both Britain and the United States. It has already sold more than eight million copies worldwide, which makes it the fastest-selling adult novel of all time. It has been bought, in a multimillion-dollar deal, by Sony Pictures and will soon become a major Hollywood film.

Books are being written and scholarly articles published to refute its more outlandish claims and theological speculations. The author’s previous three novels—Deception Point, Angels and Demons, Digital Fortress—are, as I write, second, third and fourth on the UK paperback fiction bestseller lists as well as being in the top ten in the US.

Clearly, something significant is happening here, and yet our cultural elite seem largely uninterested in the phenomenon of Dan Brown and his novel The Da Vinci Code, even though many of the most urgent political themes of our time—religious extremism, the idea that history itself is a vast conspiracy, the power of secret networks and societies over our lives, the global reach of the internet, the omnipresence of satellite surveillance and other new technologies—are present in the book.

The Da Vinci Code begins in Paris, thrillingly, with the shooting of the curator of the Louvre, Jacques Sauniere. It is night-time at the Louvre and Sauniere, in the shadow of so many masterpieces, knows that he has been fatally wounded by religious militants. In the final moments of his life, he strips naked, as you would, and uses his own blood to draw a pentacle on his chest and write symbols on the floor, before arranging his body in the form of the Vitruvian Man, from one of Leonardo da Vinci’s most celebrated sketches.

Why has he done this? It is swiftly revealed (nothing happens slowly in this novel) that Sauniere is a member of a secret society, the Priory of Sion, whose members included Sir Isaac Newton, Botticelli, Victor Hugo, da Vinci and David Icke (oh, all right, I made that last one up). He is the sole possessor of a secret that has the power to change the course of history. Unless he acts, his secret will die with him. The only man who can decode the mystery of why, though dying, he would choose to communicate so cryptically is a Harvard professor of symbology called Robert Langdon who this very night just happens to be in Paris. Langdon is awakened in his hotel room, taken by police to the murder scene and questioned as if he himself were the murderer (he and Sauniere were due to meet the following day). The police are convinced that Sauniere, at the end of his life, was trying to leave clues as to the identity of his killer. If so, and this never occurs to the good officers of the French constabulary investigating the case, why then did he not simply write down the name of the assassin?

As a career symbologist, Langdon understands the power and the allure of the arcane, the cryptic and the hidden. He knows that too often we do not know what we think we know: that we are ignorant of the essential truths—religious and political—of history. Or at least these “truths” have been deliberately kept from us by institutions such as the Catholic Church. And so begins Langdon’s quest to solve the riddle of the Da Vinci code, in which he is supported by Sophie Neveu, granddaughter of the murdered curator. Their quest leads not only to the discovery of what really became of the Holy Grail but also to the revelation of Christ’s fallen humanity: in Brown’s rewriting of church history, Christ married Mary Magdalene and together they had a child whose bloodline extends even into the present day. The Catholic Church has always known, but conspired to suppress the truth, about the tarnished divinity of Christ: his wife and the kid.

The novel, consistent with the genre, moves at a startling pace: characterisation is reduced to a perfunctory minimum, dialogue is thick with information, the blunt, staccato language is subordinate to the supercharged engine of the plot, the paragraphs are short, consciousness is represented, if at all, as a series of italicised self-interrogations, there is no ready-made formulation that Brown will not use, and each chapter ends on a moment of supreme suspense. This paragraph is characteristic: “When Aringaros switched off the phone, his heart was pounding. He gazed once again into the void of night, feeling dwarfed by events he had put into motion.”

So why are people buying The Da Vinci Code, if not for its literary refinements? The obvious answer is that, like the Harry Potterbooks that are so popular with adults, it is a hugely accomplished escapist narrative. Brown knows exactly what he is doing, what he wants to say and how to say it. Beyond its huge generic accomplishment and obvious readability, The Da Vinci Code has something else to offer: it is a fascinating political text, underscored by an intense eschatological anxiety. In the aftermath of the events of 11 September 2001 and the invasion of Iraq, in a world where a mysterious and opaque global network of religious terrorists called al-Qaeda threatens the west as well as, it is believed, communicating via encoded messages, a novel such as The Da Vinci Code carries a powerful political charge. This parable of extreme belief is about how modernity is being compromised by rivalrous pre-modern belief systems purporting to offer the absolute truth. It is also about different interpretations of the narrative of Christ: who he was, and what he meant. It explores the idea that to be modern is also to be superstitious. On another level it can be read, too, as an indictment of the secretive, opulent and corrupt Catholic Church.

“The Da Vinci Code is certainly riding the wave of revulsion against corruption in the Catholic Church,” says Richard Wightman Fox, author of Jesus in America. “What Brown’s novel taps into above all is a persistent American desire to recapture the true, original Jesus.”

Dan Brown, who is 39, was born into a comfortable middleclass family in Exeter, southern New Hampshire, where he still lives with his wife, Blythe, an art historian with whom he researches his fiction. He attended Amherst College, taught English for a period, spent several years in Los Angeles as a struggling singer-songwriter and then lived in Seville, where he studied art history. His first three thrillers were modestly received. There was nothing to suggest that his next book would be the sensation that it became; but on receiving the finished manuscript of The Da Vinci Code, his publishers, Doubleday, knew immediately that they had something special: unusually for a work by a minor novelist, more than 10,000 proof copies were sent out to booksellers. The booksellers were impressed; advance orders for The Da Vinci Code began to accumulate. Momentum was building; the rush was about to begin.

Malcolm Gladwell, in his book The Tipping Point, suggests that the best way to understand the emergence of fashion trends, the ebb and flow of crime waves, or the transformation of relatively unknown books into bestsellers, is to think of them as epidemics. “Ideas and products and messages and behaviours spread just like viruses,” he writes. So people contaminate one another with preferences and recommendations. The “tipping point” is the moment at which a social epidemic becomes contagious and crosses a threshold to reach critical mass, the point at which nothing can stop it catching on and spreading.

Dan Brown reached his tipping point when, six months after first publication, he appeared on the peak-time ABC show Good Morning America to talk about some of the issues raised in The Da Vinci Code. That day there was a surge in sales of the novel that has never really slowed down.

Today Brown seldom gives interviews, certainly never to newspapers or magazines, preferring instead to communicate via his website (www.danbrown.com). “He works every day in a writing loft,” says his New York-based agent, Heide Lange. “There’s no phone, no e-mail; he’s definitely cocooned. But he knows what’s going on in the world and could definitely hold his own in a dinner-party conversation. Yet he spends most of the time in the world of his books.”

What a strange world it is: a world of encoded artwork, anagrams, cryptic communication, astrological speculation, conspiracy theory, illuminati and symbology. Brown, this mythmaker of false reality, is a kind of benign David Icke. He evidently believes in much of what he writes about and is prepared to concede that even history itself is a conspiracy. “I began the research for The Da Vinci Code as a sceptic,” he has said. “I entirely expected, as I researched the book, to disprove this theory [of Christ’s wife and child]. And after numerous trips to Europe, about two years of research, I really became a believer. And it’s important to remember that this is a novel about a theory that has been out there for a long time ...”

The Da Vinci Codeopens with a brief mission statement. Under the single-word heading “Fact”, Brown states that the “Priory of Sion is ... a real organisation”; that Opus Dei is a “deeply devout Catholic sect that ... has just completed construction of a $47m headquarters in New York” and that “all descriptions of artwork, architecture, documents and secret rituals in this novel are accurate”. He wants us to know, then, that this is not merely a work of fantasy; it is a truthful novel, built from the bricks of fact. He also wants us to accept his scholarship: his mini-essays on the artworks in the Louvre and his pithy histories of religious sects have the smooth professionalism of a well-used travel guide and are distributed throughout the novel at well-paced intervals.

How seriously should one take Dan Brown and his often preposterous novel? We should take him very seriously indeed, not least because eight million people have bought The Da Vinci Code in less than 18 months and many millions more will do so in the months ahead. Many of these readers will enjoy the book and think no more of it; some will throw it across the room in derision. But others, judging by the number of dedicated websites it has spawned, will believe it just as some believe the astrological guides that are published each morning in the newspaper. They will believe that it is historically true. This is troubling because some of what Brown claims is true in the book—that the New Testament was a forgery, that Christ never claimed to be divine, that the Dead Sea Scrolls were discovered in the 1950s—is, in fact, false. Art historians and theologians continue to delight in tripping him up and in exposing his flawed scholarship.

Dan Brown is not, as some of his more trenchant Catholic critics would have it, a dangerous fraud, a cynical corrupter of biblical truths. What he is, rather, is a literary opportunist. He understands the underlying reasons for our eschatological anxieties and uses them in the service of a good story. And what is the reason for our present eschatological anxiety? It is, I think, this: as thinking animals we are hard-wired to seek meaning in a world that ultimately resists our attempts to explain it. Our Christian heritage and our post-Enlightenment Messianic political narratives have taught us that history has direction and purpose, that there is an end to history and a correct path to the Truth—if only, as we wander through this confusing forest of signs that is the world, we could find that path. With its pseudo-scholarship, religious zeal and conspiracy theories, The Da Vinci Code occupies the ambiguous space of all our “if onlys” while offering us its own stairway to heaven. Not a bad combination, then; in fact, a sure-fire winner.