The Difference Engine

The Difference Engine is an Alternate History novel by William Gibson and Bruce Sterling. It is a prime example of the Steampunk sub-genre.

It posits a Victorian Britain in which great technological and social change has occurred after entrepreneurial inventor Charles Babbage succeeded in his ambition to build a mechanical computer (actually his analytical engine rather than the difference engine).

The story follows Sybil Gerard, a political courtesan and daughter of an executed Luddite leader (she is borrowed from Benjamin Disraeli's novel Sybil); Edward "Leviathan" Mallory, a paleontologist and explorer; and Laurence Oliphant, a historical figure with a real career, as portrayed in the book, as a travel writer whose work was a cover for espionage activities "undertaken in the service of Her Majesty". Linking all their stories is the trail of a mysterious set of reportedly very powerful computer punch cards and the individuals fighting to obtain them; as is the case with special objects in several novels by Gibson, the punch cards are to some extent a MacGuffin.

Tropes used in The Difference Engine include:

A.I. Is a Crapshoot
Adventurer Archaeologist: Mallory is a Gentleman Adventurer Archaeologist.
Awesome McCoolname: Edward "Leviathan" Mallory, so named after the dinosaur he discovered. He doesn't much like the nickname.
Badass Bookworm: Edward Mallory is quite capable of beating up and / or shooting anyone in a fair fight. Oh, and he also discovered the largest dinosaur ever and continental drift.
Big Brother Is Watching: the Eye.
Bunny Ears Lawyer: This version of Ada is a hopeless sex and gaming addict and a bit out of her mind (though it she might have been drugged, that part's never explained).
Chekhov's Gun: Mallory notes an Awesome but Impractical 'machine-carbine' which is rather inaccurate; at the end of his story Captain Swing empties a magazine from one at him, only to miss completely and fall to a single aimed shot from Mallory's buffalo rifle.
Clockwork Creature: a literal Bamboo Technology automaton from Oliphant's Japanese visitors.
Decoy Protagonist: Mick and Sybil
Dirty Commies: The Manhattan commune, lead by noone else but Karl Marx
Divided States of America: The CSA became independent, as did Texas, California, the Manhattan commune, and Britain is playing "divide et impera".
Emperor Scientist: The merit Lords, including Brunel, Darwin, Babbage and several other famous Victorian scientists.
The Ending Changes Everything
Fan Service: in-story. The clock Mallory buys has an allegoric depiction of Science, Progress and Britain. The latter is, for some reason, wearing almost nothing. Other examples include the americans' theatre and the artists on Montmartre (described as "dressed... erm, undressed similarly to each other").
Fictional Political Party: The Industrial Radical Party, who believe in scientific endeavor, industrial progress, and meritocracy, appointing peerages to "savants".
Footnote Fever: to let the average writer read the book properly without wondering "Who the hell are those people?!"
Forbidden Fruit: The sheer possibility of receiving a fellatio makes Mallory shiver with delight after all the fantasies about it.
Genre Deconstruction: the original concept was to see how Cyberpunk themes would work in a historical setting.
Genre Popularizer: Steampunk
Good People Have Good Sex: Kind of. Lord and lady Byron have BDSM sessions and so on, while Mallory and Hetty had a very romantic night. On the other hand, Mallory's night with an Indian widow is very much Fan Disservice, for himself included.
Hand Cannon: Brian's "not exactly regulation" Russian pistol.
Hold Your Hippogriffs / Call a Rabbit a Smeerp: Many modern concepts are expressed through real and made up XIX era slang. "Clackers" instead of "hackers" with cyberpunk-like genre built around them; kinotropes instead of movie projectors, television, rotating billboards, etc.
Hooker with a Heart of Gold: Cybil and Hetty, albeit in different ways. Cybil'd been forced into that lifestyle and quit it as soon as she got the chance, Hetty is easy-going, very much enjoys sex (something that almost never happens with prostitutes) and is into prostitution only because it pays okay, unlike singing / dancing / posing which she also dabbles in.
Inferred Holocaust: the Steampunk dream of a Victorian information age is somewhat deconstructed by the heavy hints that they're using it to catalogue people for the purposes of the then-popular doctrine of eugenics.
Legacy Character: Captain Swing.
Lord Byron: is Prime Minister. Yeah.
Pretty Fly for a White Guy: The Japanese quartet can be described as extreme reverse weaboos, since they love everything western so much they want to get rid of the Japanese language.
Richard Nixon the Used Car Salesman: With Byron as Prime Minister, Benjamin Disraeli is most famous for his romance novels (he did write a couple in Real Life, including Sybil from which the Sybil Gerard/Charles Egremont storyline is taken)
Rotating Protagonist: Sybil Gerard, then Edward Mallory, then Laurence Oliphant.
Science Marches On / Technology Marches On: Many examples in-story.
Shown Their Work
Show Some Leg: Hetty also lifts her skirt when Mallory asks.
Spy From Weights and Measures: Oliphant is a travel writer, got that?
Steampunk
Twice-Told Tale: "Dandy Mick", Sybil and the Charles Egremont storyline are taken from Benjamin Disraeli's Sybil.
Unperson: Erasing people from the database does more or less that. Subverted in that it's a good thing for some (Sybil started her life anew, for one), though it's still an effective threat for law abiding gentlemen.
Very Loosely Based on a True Story: Disraeli's romantic stories. Also, whatever lies "Captain Swing" spreaded about Mallory, but that's to compromise his reputation.
What Do You Mean It's Not Heinous?: Fellatio, etc.
- Since it's Victorian England, wearing a skirt so short it shows one's lower leg when she bends over is treated in-story like if she wore a mini-skirt that doesn't cover her panties.
What If ...Charles Babbage had completed his Difference Engine (and gone on to build the Analytical Engine)?
Witch Hunt: The hunt for 'Luddite conspirators' by Charles Egremont.