The Difference Engine – William Gibson
Instead of the future this time, we have a book set in Victorian times, however Gibson (& co-author Bruce Sterling) has the Victorians achieving a lot more technological advances than happened in ‘our’ reality. As his earlier books are seen as the start of cyber punk genre, this book is similarly seen as one of the starters of the Steam Punk classification.
It took a while to get into (the jumps in narrative viewpoint can spin you out a little), and I felt the ending could have been compressed a great deal, however I’m still glad I read it.
The main split with our history is the acceptance of the multiple uses of analytical engines (though obviously mechanical, as opposed to electrical/silicone based), and therefore mass production of said items. Police (& therefore state) intelligence is compiled and used to curtail the activities of subversives, though those of high class are given a wide margin of error before any attempt to limit their activities.
Fans of American history may well be interested in this alternative playing out of events, which sees Britain strengthen their global position, to the cost of the USA.
The main aim of most of the protagonists within this story is to get their hands on a series of punch cards (that’s like a CD or hard disk drive for those unaware of how data used to be stored & processed) that don’t actually contain the routines that people assume.