One of my more embarassing habits is reading popular (and unpopular) books of pseudohistory "nonfiction," which usually involves theories of Atlantis or Ancient Astronauts. Not because I take any of it seriously...heck, I don't believe in Yoda either, and I enjoy Star Wars just fine. As a kid, I loved these books for the spookiness and mysticism, and also because in general I had a much weaker grasp of reality.
Nowadays, though, I get ironic amusement from the paranoid-schizophrenia-esque leaps in logic, the ranting crackpot prose style, the bitter denunciations of conspiratorial mainstream scientists "out to hide the truth," the desire to combine everything into one explanation a la Matt Groening's "The Nation That Controls Magnesium, Controls the Universe," and finally the author's own autistic belief in the literalism of every story.
To von Daniken's CHARIOTS OF THE GODS? every myth was a minature documentary, and we all just think it's fairytales because it was really helicopters and flying saucers and atomic weapons, instead of fairies and dragons stuff. The idea that the Ramayana or Gilgamesh may just be stories, without any literal truth never crosses his mind. Ditto for the Atlantis guys: it never once passes through their skulls that Atlantis may have been just a story or a metaphor. How is it so many people are born without a functional bullshit detector?
HOLY BLOOD, HOLY GRAIL avoids most of the pitfalls of pseudohistory: first, it's obvious these guys don't really believe it. They themselves call it "just a hypothesis." No all-caps angry ranting, no self-righteousness. For once, the obsession with secret truth hidden in art and folklore is actually relevant: if you're looking for signs of a conspiracy, it stands to reason there'd be secret symbolism in things.
Only once does HOLY BLOOD, HOLY GRAIL give in to a pratfall of historical pseudofiction, and that's in a truly excruciating blow-by-blow treatment of the Parzival story, where the highly symbolic story is treated with such literalism that it makes me wonder if the writer might suffer from autism.
I must confess, I learned a lot of real history from this book, and it was just lightly "sugared up" with obvious fantasy to make it so you don't think you're reading a textbook. Thanks to this book, I can now spot the Languedoc on a map of France, I know who Godfroi de Bullion was and what he did, and I know tons more about that fascinatingly dark and unknown period after the end of the Roman Empire, when the West was divided by tribal chieftains like the Merovingians and the Visigoths. The chapters on the Cathar heresy as well as the Merovingians are fascinating in particular, but the reason history doesn't pay any attention to the Merovingians is not because of a massive coverup, but because they just weren't that important.
The most sympathetic figure in all this, oddly enough, is Pierre Plantard, the con-artist that forged the Priory of Sion documents most of their entire theory is based on. Pierre thought it might be a way to make some quick cash if he forged a set of documents and let everybody think he was descended from Merovingian kings. When the HOLY BLOOD, HOLY GRAIL writers came to their outlandish and controversial conclusion, that the Merovingians were direct descendants of Christ, Plantard was horrified. He was a con-man, but he was a good Catholic. So, Plantard was trapped in the situation of trying to backpedal from the significance of the documents he himself forged, yet never truly able to admit his deceit.
The guys that wrote HOLY BLOOD, HOLY GRAIL also wrote my favorite Doctor Who episode, "The Sontaran Experiment." Seriously, chew on that for a second: the guy who wrote this book also wrote a TV episode about a future earth where a rubberfaced spaceman that lives in a soccer ball and his pet robot torture astronauts.