Gibson and Sterling collaborate to create an alternate nineteenth century, where Babbage's Analytical Engine has actually been built and the Information Revolution coincides with (and propels) the Industrial Revolution. Power in Victorian England has been seized by the Industrial Radical Party, with hereditary lords and Luddites alike being pushed to the sidelines.

The book is a mostly atmospheric piece with several vignettes (translation: it is a bit in want of a coherent story), that detail episodes in the lives of Londoners at the time: A prostitute who gets caught up in political spheres, a palaeontologist who stumbles upon a stack of Engine cards and into a violent riot, and a diplomat/spy who is plagued by visions of an all-seeing Eye.

In spite of the shift from cyberpunk to steampunk, the genre's typical topics are all to be found: The subculture of the tech-savvy clackers that know how to program the steam-powered Engines (using punch-cards), the dystopian view of the ever-watchful, data-gathering surveillance state, the mysterious and dangerous artefact that serves to drive the story (in this case a stack of cards created by the Queen of Engines, Ada Lovelace), even the fascination with Japan (which here has just opened itself to the world and is about to have its own Industrial Revolution).