The book and movie are (lets all say it together) fictional. Its based on an older theory which was documented in the book The Holy Blood and The Holy Grail, which I believe was retitled Holy Blood, Holy Grail for my U.S. friends, by Michael Baigent, Richard Leigh, and Henry Lincoln. It is a conspiracy theory. That is all. The physical existance of a Holy Grail is questionable and probably over exagerated. If it exists its just a cup. Doesnt matter what its made of or who used it. Also the fanatics who are looking for a direct decendant of Christ...... You aint gonna find one. The man travelled and condoms didnt exist. There is probably thousands of people out there who carry a small diluted piece of his DNA. Its been 2 thousand years for Godsake and if they do find a person carrying the Jesus gene they arn't gonna have super powers. Jesus was just an avatar. His genetics didnt make him holy, his belief did.
The idea of physically finding the Holy grail is kind of silly. However i am aware that the entire Grail myth has become a hugely important story for many people. Its power as a archetypal story should not be underrated. The Grail myth has been at the core of many European secret mystery traditions for many many centuries. Western mystic traditions have used the myth of the grail quest as the symbolic prize for mystic union, occult enlightenment and spiritual transcendence by countless students of magic and mysticism. Finding the grail itself has therefore become the final goal of spiritual alchemy. In this format perhaps the holy grail is real. It could be said to be something much more subtle than a physical relic, but infintely more powerful for the finder. I guess its pretty much like the power of Christianity itself. The real power is in the message, not in the physical remnants or artifacts. Worshipping those without understanding the message is to totally miss the mark. IMHO anyway.