The Prague Cemetery

I believe that you can reach the point where there is no longer any difference between developing the habit of pretending to believe and developing the habit of believing.

—Umberto Eco, Foucault's Pendulum.

A postmodernist Conspiracy Thriller by Umberto Eco, retelling the stories of many historical hoaxes, humbugs and forgeries - where the most important one is that of The Protocols of the Elders of Zion, which triggered the onset of anti-Semitism and was one of the indirect causes of Jews being a scapegoat for Nazi during the World War II. Considered to be one of the most controversial literary works published in the recent time because of its faithful rendition of many anti-Semitic statements, the novel is nonetheless highly popular. Its style and plot resembles those of the other novels by Eco, especially Foucault's Pendulum, where Protocols also play an important role.

The main character, Simone Simonini, is an amnesiac lawyer working theoretically as an antiquary and practically as an informant for the intelligence service and a forger of documents. His mind is full of partial memories, racial and religious prejudices and conspiracy theories based on them - and though he is not always sure of the difference between them, he manages to make a decent amount of money by using them creatively. Besides obvious problems connected with his profession he must deal with a nosy priest who has a habit of breaking into his house and leave notes in Simone's own diary, implying that he knows more about Simone's life than Simone himself. Oh, and there is also a cellar full of corpses, a hysteric woman with two personalities, and bunch of cultists worshiping Satan - all that on the background of Franco-Prussian War, the movement of Garibaldi, and The Gay Nineties.

Tropes used in The Prague Cemetery include:

Amnesiac Liar: Simone Simonini.
Because I'm Good At It: it is true that Simonini's job implies many unethical activities, but he didn't really have a choice after he was practically forced to become an apprentice for a forger lawyer who disinherited him.
Believing Their Own Lies: happens to Simonini from time to time.
Blackmail Is Such an Ugly Word: conversations between Simonini and many of his employers.
Chronic Backstabbing Disorder: Simonini is a severe case.
Chronic Villainy: Simonini. Even after the happy ending (From a Certain Point of View) it's hard for him to cope with what he perceives as 'inactivity'.
Conspiracy Kitchen Sink.
Conspiracy Theories: as a result of the events described in the novel.
Evil Plan: plenty of them.
Freudian Excuse: the leitmotiv of Simonini's childhood are his father musings on evil Jesuits and, on the other hand, those of his grandfather, which concern Jews.
He Knows Too Much: happens to a lot of people.
Historical Domain Character: Sigmund Freud, Giuseppe Garibaldi and Alexandre Dumas - to name only a few. In fact, as Eco underlines in interviews, ALL characters with the exception of Simonini and minor figures from his past are historical.
Historical In-Joke: quiet a lot of them.
Hysterical Woman: Diana Vaughan.
Identity Amnesia: Simone Simonini and Fr. Dalla Piccola.
The Infiltration: Simonini performs it many times, most notably pretending to be a follower of Garibaldi to discredit him.
The Informant: Simonini himself.
Luxury Prison Suite: very important for Simonini, considering his love of good cuisine.
Make It Look Like an Accident.
Malicious Slander.
Manipulative Bastard: Simonini and, well, almost every other character.
Note to Self:: strongly subverted, as Simonini suspects that he and Dalla Piccola are the same person - and shares with him this suspicion - but cannot be sure for a long time.
Number of the Beast - repeatedly told by the children present at the black mass.
Ominous Opera Cape: the cover of most editions features a model case.
Plagiarism in Fiction: a very sophisticated case.
Propaganda Machines: decidedly in plural.
Shout-Out: most notably to Italo Calvino and to Dumas's Joseph Balsamo - not only does Eco make Simonini explicitly refer to this book (and meet its author) but also places in the novel many plot references to Dumas's book.
Shown Their Work: actually, Eco's scholarly essays in which he mentions Protocols can be very useful in grasping the meaning of the events in the novel.
The Shrink: Freud, Charcot, Bourru, Burot and Du Maurier.
Sophisticated As Hell: as can be expected from Eco.
Split Personality: Simonini.
Inner Dialogue: Simonini.
Through the Eyes of Madness: to some extent, Simonini's point of view.
Unreliable Expositor: many of them.
Unreliable Narrator: an elaborated case. The Narrator, who admits that he is trying to put together the relations of Simonini and Dalla Piccola (thus resembling a historian, but also a reader), is nonetheless conscious that the solution must involve arbitrariness.
Unwitting Pawn: almost everyone who meets Simonini, and quite often Simonini himself.
Viewers Are Geniuses: characteristic for Eco's novels.
Villainous Glutton: Simonini. If there is anything he loves, it is food.
You Have Outlived Your Usefulness: the main reason of murders committed by Simonini.
Your Head Asplode: the death of Joly.

Tropes in conspiracy theories believed in or launched by the characters:

Ancient Conspiracy: more than one.
Corrupt Church: especially Evil Jesuits.
Demon Lords and Archdevils: worshipped by the Diana's sect.
Evil Smells Bad: Simonini quotes the fragment by Victor Hugo about Jews to substantiate it.
Final Solution: appears in one of the dialogues as an allusion to the future meaning of Protocols in history.
Greedy Jew: one of the reappearing stereotypes.
Jewish Complaining: Simonini's impression after some conversations.
The Knights Templar: mentioned in passing.
Literary Agent Hypothesis.
Nebulous Criminal Conspiracy.
The Omniscient Council of Vagueness.
Religion of Evil: Palladism.
Secret Circle of Secrets.
Take Over the World: the goal of almost everyone.
Theory of Narrative Causality: Simonini adjusts his theories to the customers who pay for them.