Series
The Robert Langdon series has 5 books.
Published between 2000 and 2013, in the same order they are meant to be read.
Robert Langdon is Dan Brown's series of thrillers following a Harvard professor of symbology: Angels & Demons, The Da Vinci Code, The Lost Symbol, Inferno, Origin and The Secret of Secrets. Each book is a self-contained mystery and can be read alone, but Angels & Demons comes first, and reading in order lets Langdon's history accumulate.
All 5 books total 3,161 pages.
The Books Oracle — track the series you are partway through, and see what to read next.