The DaVinci Code is good fiction with some truths, takes a lot from The Holy Blood and the Holy Grail which is in my opinion a more historically accurate book....though I believe that ain't the full story either.
The best book on Freemasonry is Masons by Gioele Magaldi, though it isn't a fun read it is filled with real info. Magaldi is a Mason so he's biased, but he admits many Freemason lodges turned tyrannical, corrupt and evil in this last century.