The instance that prompted me to write this was when Robert Langdon was explaining the Illuminati Symbolism on a US $1 bill. For background, the Illuminati is an historical secret society which Angels & Demons claims is the anti-Church "inner circle" of the Freemasons.
Robert Landon explains that the reverse of the Great Seal of the US printed in the back of the bill (the pyramid side) is actually an Illuminati symbol. He continues to explain the meaning of the latin.
Vittoria seemed startled. She glanced down at the bill again. "The writing under the pyramid says Novus... Ordo..."
"Novus Ordo Seclorum," Langdon said. It means New Secular Order."
"Secular as in nonreligious?"
"Nonreligious. The phrase not only clearly states the Illuminati objective, but also blatantly contradicts the phrase beside it. In God We Trust."
Langdon then explains (truthfully) that the symbol was put there by FDR, a known freemason.
Sounds convincing, right? Unfortunately, the Latin phrase means "New Order for the Ages" and FDR just copied the Great Seal of the United States that has existed since 1782, 14 years before Freemasons started using the symbol. See Official 1782 Explanation of the Great Seal for more information.
Now, of course Dan Brown writes these books as lightweight fiction to appeal to the masses so such truth-twisting is tolerable. What bugs me, though, is the combination of the unavoidably-sympathetic, brilliant Harvard professor who tells us these lies and Brown's never-ending digs at the Christian Church found both in The Da Vinci Code and in Angels & Demons. It seems to me that he is exploiting his engaging writing style for more nefarious purposes than producing a best-selling book.
But maybe I'm just a conspiracy theorist.