The Difference engine is a 1990 steampunk novel co authored by William Gibson and Bruce Sterling.
In a departure from the two authors speciality in the cyberpunk genre, the novels plot takes place in an alternate late 19th century in which Charles Babbage's mechanical computer (the titular "Difference Engine") was considerably more successful than it was in our reality, thus starting the computer revolution at least 100 years earlier than it occurred in our "prime" universe.
As such, the British Empire became considerably more powerful than it did in actuality, and the use of these early computers has kick started a social revolution within the empire, where the hereditary peerage system has been scrapped and replaced with a meritocracy which actively promotes learning and speciality in the "practical" sciences, as such, figures such as Isambard Kingdom Brunel, Charles Babbage and Lord Byron occupy high places within the government (with Byron being the Prime minister for most of the novel after deposing the Duke of Wellington who had seized power in a violent coup d'etat).
The closest rival that the British Empire faces is France, who also have their own computers (which they call "Ordinateurs"), and in this reality, the United States is made up of a series of smaller countries, all of whom don't particularly get on with each other, named ones include the "Union of States", the "Confederate States of America", "The Republic of Texas" and the "Manhattan Commune" (a communist state which occupies most of new york state).
The plot of the book itself is made up of a series of vignettes, each one concentrating on a series of characters who fit in with the overall story arc, this overall story arc concerning the ownership of a box of punch cards containing a computer program, the use of which is speculated about by many of the characters but only actually revealed in a small paragraph right at the end of the book, meaning the punch cards simply act as a "mcguffin" of sorts, with no effect on the plot other than the fact that they exist.
The vignettes are usually prefaced by some sort of passage, written in the style of a police report, a news report or a diary entry from one of the other characters explaining the setting and background to the events, before the storyline begins proper.
This can be somewhat confusing in places, as the books overall plot does not strictly follow a linear time line, and the prose itself is written fully in the style of how it would have been written and spoken in the 19th century, thus it contains many archaic terms and turns of phrase that the uninitiated reader may struggle to make sense of, as well as some forms or social etiquette which have long since fallen out of use but which were quite common at the time.
It should also be pointed out that although this book is set in the "prim and proper" Victorian era, it does indeed contain numerous sexual scenes, described in detail, most notably occurring during the sections dealing with the character "Edward Mallory".
All in all, the novel is a fairly good piece of alternative history fiction, albeit a difficult one to read, and will require some research being done for those who are not familiar with the time period or the concepts being discussed.