I'm reading Umberto Eco's Foucault's Pendulum again!
It's been about 10 years aince I last read it
It's about a bunch of people who come up with the ultimate conspiracy theory - in their first abortive attempt they come up with Jesus didn't die but married Mary Magdalean and founded the French Royal family - familiar?
One of them says something like " It's been done, holy blood, holy grail, what a load of rubbish you'd never sell more than a thousand copies of that"
The whole book revolves around people's willingness to believe conspiracy theories - Eco must have been rolling about laughing when the Da Vinci code came out