I saw da Vinci after I read the book. I have to agree with the poster who said it was very similar to National Treasure. It's also similar to many thrillers where the hero seeks some lost secret while a mad killer stalks him. Add in the hero's girl and we must have several hundred variations written on the same basic plot.
It's an easy task. Get one hero, one girl, one killer, one secret, and one conspiracy. Then hide the secret, start the hero after it (with girl in tow), send the killer after the hero, and reveal bits of the conspiracy as the action proceeds. At the end, find the secret, kill the killer, thwart the conspiracy, and hero gets girl. This basic story is one of our cultural legacies.
Indiana Jones and the Last Crusade!