Angels & Demons is a 2000 bestselling mystery-thriller novel written by American author Dan Brown and published by Pocket Books. The novel introduces the character Robert Langdon, who is also the protagonist of Brown’s subsequent 2003 novel, The Da Vinci Code, and 2009 novel, The Lost Symbol. It also shares many stylistic literary elements with its sequel, such as conspiracies of secret societies, a single-day time frame, and the Catholic Church. Ancient history, architecture, and symbolism are also heavily referenced throughout the book. A film adaptation was released on May 15, 2009, though it was set after the events of The Da Vinci Code film, which had been released in 2006.