Religious corruption
Dan Brown's works are well-known to stir up controversies with their focus on modern corruption in the Catholic Church. This theme is seen in Angels and Demons prominently in plot details such as the Pope's sympathies toward science, the Pope's breach of vows, the Illuminati's infiltration of the papacy, the murders of Cardinals to manipulate the future papacy, and the murder of the Pope.
As well, the Camerlegno is revealed to be the mastermind behind the attempted terrorist attack on the Vatican City, so deeply religious that he pushes himself to the point of radicalism. He not only poisons the Pope after learning he fathered a child, he killed the preferiti in an intricate plan to present religion as the superior ideology. After it's revealed that the Pope did not break his vow of celibacy to father a child, Ventresca's radicalism and hypocrisy is finally revealed.
The effect of this theme renders the reader skeptical of institutions that are classically images of moral uprightness and trustworthiness. This is a genre enhancing theme as well, in that it encourages the reader to feel a sense of tension between all of the parties involved in Angels and Demons.
Secrets revealed through clues
This is a staple in the mystery genre. The knowability of mysterious elements within the plot leads the reader to guess "who-done-it." In Dan Brown's narrative, the typical clue schemas are less pronounced, as Brown prefers symbols and codes to outright clues. His clues are often pronouncedly more skepticizing and rooted in corruption and conspiracy.
Conspiracy theories
Conspiracy theories are notably pronounced in Angels and Demons and included corruption of the Catholic church even in Vatican City. The Illuminati conspiracy has gained an incredible following in pop-culture through Brown's fiction, and is often thought of as the catch-all conspiracy. Within this work, conspiracy theories are actualized, allowing the reader to exercise a cynical and suspicious view of the powers that be.
Religion Versus Science
Angels and Demons has a basis in the age-old debate between religion and science. While religion suggests that by supporting science we are letting go of our spirituality and belief, science debates that with religion we underestimate, and even kill our potential. The characters are often seen in a fix on which side to support. Leonardo Vetra, a priest and scientist, was murdered as a result of this debate. Highly religious people like Ventresca shudder at the thought of a love affair between a priest and a nun even though it was not physical. Then, people like Kohler condemn religion as he was denied medical aid as will of the God. The events of the book seem like an attack on religion by science, but at the end, it's revealed that the Camerlengo carefully designed it to condemn science and hold religion as the superior ideology.
