<P> 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 ." </P> <Table> <Tr> <Th> No . </Th> <Th> Title </Th> <Th> Identifier (s) </Th> <Th> Date of publication </Th> <Th> Summary </Th> </Tr> <Tr> <Td> </Td> <Th> Angels & Demons </Th> <Td> ISBN 1 - 59315 - 140 - 3 </Td> <Td> May 2000 </Td> <Td> Following the murder of a physicist, Leonardo Vetra, a symbolist, Robert Langdon, and a scientist, Vittoria Vetra, are on an adventure involving a secret brotherhood, the Illuminati . Clues lead them all around the Vatican, including the four altars of science, Earth, Air, Fire and Water . </Td> </Tr> <Tr> <Td> </Td> <Th> The Da Vinci Code </Th> <Td> ISBN 0 - 385 - 50420 - 9 </Td> <Td> April 2003 </Td> <Td> Secret of the Holy Grail . In the novel, Sir Leigh Teabing explains to Sophie Neveu that the figure at the right hand of Jesus in Leonardo da Vinci's painting The Last Supper is not the apostle John, but actually Mary Magdalene . </Td> </Tr> <Tr> <Td> </Td> <Th> The Lost Symbol </Th> <Td> ISBN 978 - 0 - 385 - 50422 - 5 </Td> <Td> September 2009 </Td> <Td> A thriller set in Washington, D.C., after the events of The Da Vinci Code, and relies on Freemasonry for both its recurring theme and its major characters, which included Robert Langdon . </Td> </Tr> <Tr> <Td> </Td> <Th> Inferno </Th> <Td> ISBN 978 - 0 - 385 - 53785 - 8 </Td> <Td> May 2013 </Td> <Td> Robert Langdon wakes up in a hospital bed suffering from amnesia . A woman tries to kill him and he is saved by a doctor, Sienna . Robert finds links to Dante's Divine Comedy in all the messages projected by the canister and uses his knowledge of symbology to reach Venice where he believes he will find the cave . </Td> </Tr> <Tr> <Td> 5 </Td> <Th> Origin </Th> <Td> ISBN 978 - 0593078754 </Td> <Td> October 2017 </Td> <Td> TBA </Td> </Tr> </Table> <Tr> <Th> No . </Th> <Th> Title </Th> <Th> Identifier (s) </Th> <Th> Date of publication </Th> <Th> Summary </Th> </Tr>

Which book is first the davinci code or angels and demons