What makes The Da Vinci Code an international bestseller?

The arrival of Alex Hamilton's year-end paperback fastsellers table for 2004 makes it a good moment to examine the publishing phenomenon of the year. Dan Brown's The Da Vinci Code has been a worldwide bestseller, with more than nine million sold in the US and the same commercial success repeated in translation across the world. It topped Hamilton's Guardian list with numbers that have only been matched by Lady Chatterley's Lover in the 60s, James Bond in the 70s and Harry Potter in the 21st century.

So what is it about this popular thriller that has appealed to so very many readers? It's a rich mix of conspiracy theories, including those relating to Opus Dei and the Priory of Zion, not to mention the idea that there are descendants of Jesus whose identity has been kept secret over the years. Those readers with longer memories will recall a similar brew in the non-fiction bestseller The Holy Blood and the Holy Grail, and perhaps it's not surprising that the authors of that book are threatening to sue Dan Brown for plagiarism. It certainly looks as if embedding these old chestnuts in a thriller plot for a new generation has been a pretty successful idea. His book Angels and Demons gave an energetic revival to the myth of Illuminati.

It's worth looking more closely at Brown's writing though. Many commentators have described it as terrible, but also admitted that they couldn't put the book down. And it is the sheer page-turning quality, linked to the ability to end each chapter on a cliff-hanger, which is what you most notice about the book. The characters make cardboard cut-outs look substantial, but the action glues you to the page. Brown's thrillers also enjoy that rare crossover for the thriller from the smallish male market into the much larger female readership. Women pass books along and recommend them widely, thus keeping the ball rolling and explaining why the book has gone on selling strongly throughout the year, with 82,797 copies sold in the week before the mad Christmas rush. It's the first fiction title to top the UK Christmas charts for five years and not an obvious Christmas present, except perhaps as a stocking-filler from avid fans of the book.

Amanda Ridout of HarperCollins said: 'My interpretation of Brown's success is that it makes people feel a lot cleverer in very short chapters. Also people adore conspiracy theories.' David North, MD of Macmillan, expressed a commonly held view amongst other publishers contemplating Brown's domination of the bestseller lists with this and his other titles: 'At first we thought of him as Dan Brown, but it became Dan Bloody Brown. We have authors who expect to be number one, and we had to say to them: "You're doing very well. You're number five."'

Would-be commercial thriller writers should analyse what makes Brown's books work. There's certainly nothing new about the content or scintillating about the writing, so it looks like it's the compelling page-turning plots which are making these books into such huge bestsellers.