Angels an Demons is a bestselling mystery novel by Dan Brown. Published in 2000, it introduces the character Robert Langdon, who is also the principal character of Brown's subsequent, better-known novel The Da Vinci Code. It also shares many stylistic elements with the better known novel, such as conspiracies of secret societies, a single day time frame and the Roman Catholic Church. The story involves a conflict between an ancient group, the Illuminati, and the Roman Catholic Church. A film adaptation is due for release on May 15, 2009.