For those who liked the Da Vinci Code you might want to try Foucault's Pendulum by Umberto Eco.

Here is one reader's review of it as posted on amazon.com

This book has it all! Mystery, thriller, suspense, world history, masons, world conspiracy, voodoo, magic, computers trying to reproduce the true name of God, jewish mysticism , druids of the forests, underground tunels that connect strategic points of the planet, publishers and writers, knights of the temple, action all around the world through the past 2 milenia. YOU NAME IT. Centuries of conspiracy and battle for the domination of the world , unspeakable secrets passed upon generation to generation from a few chosen ones, build up until the last climactic pages of the book.
ADVICE:

The book is really worth for its money and it will keep you awake for a few days. You will refuse to close the book until you reach the end. In the beginning you will not understand a thing, what is going on, who are these people, what are they trying to do. Never mind, just carry on. Eco meant the book to be this way! Enjoy the book and if you dont understand some historical remarks never mind, just continue, dont stumble upon the little details and the dates, get the big picture. You will have plenty of time to think about it after you have finished but the main thing is to go entirely through the book and finish it. It will leave you with your mouth open. Dont let yourself think :I cant understand this, I am an idiot therefore I will not continue. No, just finish the book , at the end you will be rewarded as is the case with all of Ecos books. After all there is no such thing as "I dont understand the book", there is only "I didnt let myself free enough to understand it".

Eco writes his books this way, they are only meant for the strong of spirit, people with perseverance that are willing to strugle in order to reach the ultimate truth that only the very few have mastered. His novels are deliberately cryptic but only to the point that they discourage the faint of hurt. For the few strong men that are willing to engage into the battle, all the mysteries and the hypes reveil themselfs at the end,like the petals of a rose in the spring. This is the REWARD, something central on Eco's novels.

IN ORDER TO PROVE MY POINT ECO HIMSELF ADMITTED that he included the first hundred pages of pure history in the "Name of the Rose" just to discourage the readers that would not have the strenght to continue with the book. That was the PRICE! that the readers have to pay in order to reach the monastery up in the mountains that the story takes place. His editor suggested that he should completely remove this big part of the book but Eco denied!

Going back to the PENDULUM, You should never forget that this book is a really mystery book. Not only for the heros of the book but also for you , the reader. There were times that I felt that I was involved in this world conspiracy and I may be in danger like the hero of the book. That is the trully amazing element of Eco. It gets the reader involved. And at the end you will have a completely different point of view about the world.

Eco has said that the ultimate mystery book is the one that the READER is himself the killer!

I definetely recommend the book, it will not dissapoint you.

Enjoy!

Trully the book is awesome. I read the book before seeing the movie.