Question: Robert Langdon's films based on Dan Brown's novels were released in a different chronological order than the novels, though the last movies released was also the last book released. Which book was it?
Context: Angels & Demons is a 2009 American mystery thriller film directed by Ron Howard and written by Akiva Goldsman and David Koepp, based on Dan Brown's novel of the same name.  It is the sequel to the 2006 film "The Da Vinci Code", also directed by Howard, and the second installment in the "Robert Langdon" film series.  The novel was published first and "The Da Vinci Code" novel followed it.  Filming took place in Rome, Italy, and the Sony Pictures Studios in Culver City, California.  Tom Hanks reprises his role as Professor Robert Langdon.  Producer Brian Grazer, composer Hans Zimmer and screenwriter Akiva Goldsman also return, with David Koepp coming on board to help the latter. Daniel Gerhard "Dan" Brown (born June 22, 1964) is an American author of thriller fiction, most notably the novels "Angels & Demons" (2000), "The Da Vinci Code" (2003), and "Inferno" (2013).  Brown's novels are treasure hunts set in a 24-hour period, and feature the recurring themes of cryptography, keys, symbols, codes, and conspiracy theories.  His books have been translated into 52 languages, and as of 2012, sold over 200 million copies.  Three of them, "Angels & Demons" (2000), "The Da Vinci Code" (2003), and "Inferno" (2013), have been adapted into films. Robert Langdon is a fictional protagonist of a series of novels, novellas and short stories by American author Dan Brown.  A Harvard University professor of religious iconology and symbology (a fictional field related to the study of historic symbols, which is not methodologically connected to the actual discipline of semiotics).  Brown's novels that feature the lead character Robert Langdon also include historical themes and Christianity as motifs, and as a result, have generated controversy.  Brown states on his website that his books are not anti-Christian, though he is on a 'constant spiritual journey' himself, and says that his book "The Da Vinci Code" is simply "an entertaining story that promotes spiritual discussion and debate" and suggests that the book may be used "as a positive catalyst for introspection and exploration of our faith." Professor Robert Langdon is a fictional character created by author Dan Brown for his "Robert Langdon" book series: "Angels & Demons" (2000), "The Da Vinci Code" (2003), "The Lost Symbol" (2009), and "Inferno" (2013).  His newest novel "Origin" is going to be published on October 3, 2017.  He is a Harvard University professor of religious iconology and symbology (a fictional field related to the study of historic symbols, which is not methodologically connected to the actual discipline of semiotics). The Va Dinci Cod: A Fishy Parody is a parody of the New York Times Bestseller "The Da Vinci Code".  It was written by British critic and novelist Adam Roberts under the pen name Don Brine (a parody of Dan Brown).  The character names in the novels are reminiscent of the well-known characters: Sophie Nudivue (Sophie Neveu), Robert Donglan (Robert Langdon), and Curvy Tash (Bezu Fache).  It was published in 2005 by Harper Collins. Angels & Demons is a 2000 bestselling mystery-thriller novel written by American author Dan Brown and published by Pocket Books and then by Corgi Books.  The novel introduces the character Robert Langdon, who recurs as the protagonist of Brown's subsequent novels.  "Angels & Demons" 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 symbology are also heavily referenced throughout the book.  A film adaptation was released on May 15, 2009. " The Da Vinci Code" film had been released in 2006. The Robert Langdon films are a series of American mystery thriller movies directed by Ron Howard.  The films focus on the eponymous professor, a fictional character appearing in a series of novels by author Dan Brown.  The film series has a different chronological order than the novels, and consists of "The Da Vinci Code" (2006), "Angels & Demons" (2009) and "Inferno" (2016).  The series has grossed almost $1.5 billion worldwide. The Da Vinci Code is a 2006 American mystery thriller film directed by Ron Howard, written by Akiva Goldsman, and based on Dan Brown's 2003 best-selling novel of the same name.  The first in the "Robert Langdon" film series, the film stars Tom Hanks, Audrey Tautou, Sir Ian McKellen, Alfred Molina, Jürgen Prochnow, Jean Reno, and Paul Bettany.  In the film, Robert Langdon, a professor of religious iconography and symbology from Harvard University, is the prime suspect in the grisly and unusual murder of Louvre curator Jacques Saunière.  In the body, the police find a disconcerting cipher and start an investigation.  A noted British Grail historian named Sir Leigh Teabing tells them that the actual Holy Grail is explicitly encoded in Leonardo da Vinci's wall painting, "The Last Supper".  Also searching for the Grail is a secret cabal within Opus Dei, an actual prelature of the Holy See, who wishes to keep the true Grail a secret; the revelation of this secret would certainly destroy Christianity. Inferno is a 2016 American mystery thriller film directed by Ron Howard and written by David Koepp, based on the 2013 novel of the same name by Dan Brown.  The film is the sequel to "The Da Vinci Code" and "Angels & Demons", and is the third installment in the "Robert Langdon" film series.  It stars Tom Hanks, reprising his role as Robert Langdon, alongside Felicity Jones, Omar Sy, Sidse Babett Knudsen, Ben Foster, and Irrfan Khan.  Together with the previous film, it remains Hanks' only live-action sequel. Inferno is a 2013 mystery thriller novel by American author Dan Brown and the fourth book in his Robert Langdon series, following "Angels & Demons", "The Da Vinci Code" and "The Lost Symbol".  The book was published on May 14, 2013, ten years after publication of "The Da Vinci Code" (2003), by Doubleday.  It was number one on the "New York Times" Best Seller list for hardcover fiction and Combined Print & E-book fiction for the first eleven weeks of its release, and also remained on the list of E-book fiction for the first seventeen weeks of its release.  A film adaptation was released in the United States on October 28, 2016.
Answer: Inferno