Many people don't know (because the movies didn't follow the books) that Angels and Demons by Dan Brown was the first book to feature Robert Langdon. Langdon is a Harvard Professor of Religious Iconology and Symbology. This makes him more than your average professor. 

 

Very quickly Robert Langdon is thrown into a situation where only his expertise in the subject of Symbology and Religion can help and he is called upon to give some insight into a mysterious symbol. The fact that it has been seared into the chest of a murdered physicist and a makeshift bomb has been stolen in the process, makes the matter quite pressing. Much to Langdon's surprise, he knows the symbol; it is one of the symbols associated with an ancient secret brotherhood known as the Illuminati. 

 

This book is a great introduction to Dan Brown's work; it isn't as controversial as The DaVinci Code but it does introduce you to the way Dan Brown's books work and now they have a sense of conspiracy theory to them. Please keep in mind that this book too is one you have to read with an open mind. Dan Brown prides himself on making people stop and think and plays on many conspiracy theories and brings them to life. If you find that you don't enjoy that type of thing or exploring the "possibilities" this book and most of Brown's other books are probably not your cup of tea.