Codex 632, by Jose Rodrigues Dos Santos.
This book follows, in novel form, the exploration of who really discovered America and who the man known to the world as Christopher Columbus truly was. The book opens with the death of a historian who has just discovered explosive information regarding Columbus, information that will change the world's view of the discovery of America, and follows the efforts --ultimately successful -- of a second historian to disentangle and decode the first man's research and find out what he had learned before his untimely death.
This books has elements of the Da Vinci Code in it, but really is much more intellectual than the Da Vinci Code. If you are not prepared to wade through a large amount of scholarly writing, then this book is probably not for you. Personally, I found it fascinating and eye opening. Not only did it involve puzzles and riddles, as well as an interesting plot line, it also educated me on code-breaking, kabbalism, and above all on the age of discovery and Christopher Columbus. I admit that this book may take a bit of work to get through, but I found it worth every second and every ounce of mental effort. I cannot recommend this book highly enough. 5 out of 5.