Dan Brown stated in his fact section
“The Vatican prelature known as Opus Dei is a deeply devout Catholic sect that has been the topic of recent controversy due to reports of brainwashing, coercion, and a dangerous practice known as “corporal mortification.” Opus Dei has just completed construction of a $47 million World Headquarters at 243 Lexington Avenue in New York City.”
Silas the albino Monk is supposed to be a member of Opus Dei. The self mutilation he endures heightens the sinister nature of the character. Opus Dei has a response to the allegations in the Da Vinci code at their web site.
Typically in the Da Vinci Code organizations and rituals have been dramatically sensationalized.