Foucault's Pendulum by Umberto Eco (1988)

This is a brilliant book, once you understand it. I must confess, I found it heavy reading, but then I read it again, and then again, and slowly realized what a brilliant book it is. Foucault's Pendulum is a book that delves into conspiracy theories, but the concept in the book is more about detailing how weird conspiracy theories can be, how they can drive people totally delusional, and so on. As a side note, the book is nothing like the much more popular 'The Da Vinci Code' by Dan Brown (that dealt with real life conspiracy theories while "Foucault' Pendulum" is more about how conspiracy theories are bunkum, but have enough adherents to provoke strange reactions in people, especially in people who have bought into such theories. Foucault's Pendulum by itself does not promote a conspiracy theory, but integrates many prevalent theories related to the Knight Templars, Freemasons, The Elders of Zion, The Cabalists, The Jesuits, The Bavarian Illuminati, and many others, and adds one more fictional cult of its own - a fictional secret society called the Tres (Templi Resurgentes Equites Synarchici, Latin for the nonsensical "Synarchic Knights of Templar Rebirth").



The name of the book is fascinating in itself, talking about the famous experiment by the French physicist Léon Foucault, in the year 1851, in the Meridian Room of the Paris Observatory. This experiment involved hanging a tall pendulum free to oscillate in any vertical plane; over a period of time, the paths taken by the pendulum will demonstrate the rotation of the earth (Wikipedia); this device forms an integral part of 'The Plan' described in the book.
The book is itself about these 3 characters, Belbo, Diotallevi and Casaubon (the narrator, describing the events in flashback), who get interested in conspiracy theories, the occult and decide to prepare their own theory called 'The Plan'. Their personal histories are described in detail, including their earlier review of a book on the 'Knights Templar' which describes how the holy warriors did not totally die out when they were suppressed by the French Emperor and the Pope, but instead the remnants of the order went underground, established cells throughout the world in order to eventually take over the world and avenge their destruction. Their are other experiences of interaction with occult ideas and other conspiracy theories.
Eventually, the 3 develop their own conspiracy theory that includes many elements, and weaves together an intricate web, taking the help of the personal computer of Belbo (called 'Abulafia'). Eventually, they start attracting the attention of a secret brotherhood that imagines itself to be secret society described in this plan, and which wants to capture these 3 authors for learning more about what they know, and capture Belbo in order to force him to reveal more. This eventually leads to his death at the hands of the gang when he is unable to provide them more information.
Casaubon escapes, and is left thinking about what they have created, and when he will be eventually captured by this society. He is clear that he will not let them believe that 'The Plan' is real.