I am sure most people know the basic plot of the book (Robert Langdon gets blamed for the murder of a curator of the Louvre, works with Sophie Nevau - the curator's granddaughter - to figure out the message he was trying to leave her). The thing I find most interesting is the secret societies, the codes and messages left by the curator and the suspense of not knowing who or what they are looking for or are looking for them.Here is my personal opinion/disclaimer on this novel:
This is a story. It is a novel and the author has written it very realistically. Dan Brown incorporates parts of art history, church history and architecture, into a story that leads the reader through many landmarks of Europe. However, much of the driving plot points are not true. How many are true? I am not sure. But I do know that some of the major key points (what the Grail is, the groups protecting and attempting to destroy the Grail) are not based on fact and they are not proven - if they are provable at all.
All in all, I say The Da Vinci Code is a great read for people who enjoy suspense and mystery. Just remember: it is a story, but it is a good story!