The Robert Langdon books by Dan Brown consist of four (to date) fast-paced thriller/suspense novels, featuring fictitious genius Harvard symbology and iconology professor, Robert Langdon. I have read the first three: Angels & Demons, The DaVinci Code, and The Lost Symbol. Each book takes place in a famous city, involves a secret society of a religious or occult nature, and includes a new female counterpart with Langdon.
Angels & Demons is a murder mystery taking place in Vatican City, where Professor Langdon must save the day to stop the murders of Catholic Cardinals inflicted by a mysterious, archaic secret society, called the Illuminati.
Lastly, The Lost Symbol is a scavenger hunt across Washington, D.C., leading to a hidden message left by the Freemasons. In each book, Langdon and his female counterpart encounter a series of clues. Langdon must then use his expertise in interpreting symbols and icons to solve them. The FBI or Secret Service is usually involved, as is some breaking-edge scientific technology: in Angels & Demons, it is an antimatter bomb; in The Lost Symbol, it’s a scientific invention that weighs (therefore proving the existence of) the human soul.
The Robert Langdon books are fun, plot-driven thrillers designed to twist and turn in all the right places. Angels & Demons and The DaVinci Code in particular were a blast. The ending of The Lost Symbol fell flat for me.