Brown's latest thriller (after Angels and Demons)is an exhaustively researched page-turner about secret religious societies, ancient coverups and savage vengeance. The action kicks off in modern-day Paris with the murder of the Louvre's chief curator, whose body is found laid out in symbolic repose at the foot of the Mona Lisa. Seizing control of the case are Sophie Neveu, a lovely French police cryptologist, and Harvard symbol expert Robert Langdon, reprising his role from Brown's last book. The two find several puzzling codes at the murder scene, all of which form a treasure map to the fabled Holy Grail. As their search moves from France to England, Neveu and Langdon are confounded by two mysterious groups-the legendary Priory of Sion, a nearly 1,000-year-old secret society whose members have included Botticelli and Isaac Newton, and the conservative Catholic organization Opus Dei. Both have their own reasons for wanting to ensure that the Grail isn't found. Brown sometimes ladles out too much religious history at the expense of pacing, and Langdon is a hero in desperate need of more chutzpah. Still, Brown has assembled a whopper of a plot that will please both conspiracy buffs and thriller addicts.