In 2003 a little-known author named Dan Brown published a sensitive, lyrical literary novel called The Da Vinci Code, which achieved critical success but only modest sales. Ha. O.K., Brown's follow-up thunders into bookstores in September, reuniting legions of symbology-starved fans with their spiritual leader, Robert Langdon. The bar is both low and high for this book: it will sell jillions of copies (the first printing alone is rumored to be over 6 million), but it will have to outperform its predecessor in order not to be judged a disappointment no mean feat. Little is known about the book, except that it follows 12 hours in the life of Langdon and that it takes place in Washington, D.C., and involves Freemasonry. And also, probably, a symbol. That has been lost.