Strategerist - I read "Foucault's Pendulum" too and I agree! Every other chapter was excruciatingly dull - Eco really needed to hire an editor for that one.
But it had its moments - just miss out all the chapters to do with S American orixias. Plus there was a slightly cool bit near the end: to paraphrase - why waste your time with occultism, when you can touch Christ's Body in any Church? But Eco didn't exactly make the idea fly.
The parts where Jacopo Belbo was flashing back to WWII in his village were really pointless and dull...
Indeed, it probably could have been cut by 1/3rd.
I believe Pendulum was his first book after the surprise smash hit The Name of the Rose so perhaps they were afraid to really edit him.
It's really an encylopedia of history on all these various groups...Templars, Rosicrucians, Bavarian Illuminati, Assassins...that people get curious about.