In this book Ranciere describes the genesis of modern socialism in the minds of the workers of early C19th France by reference to worker writers of the time. The worker writers express desires that are shockingly different from the Socialism that came into being and this is Rancieeres core thesis and probably why the book has been so thoroughly ignored for all these years. Basically it builds a devastating critique of socialism that suggests that it became divorced from the desires of the class it was mean to liberate.
This is an important book and one in which Ranciere does not parade his knowledge of the classics, but writes clearly to amplify the many quoted passages by the workers themselves. Although the period in which the workers were writing was on the cusp of industrial modernism in Paris the ideas are relevant and fresh in todays post-industrial crises and precarity.
The radical shift that Ranciere suggests is from an wholly economic analysis to one that focuses on human intellectual interiority as the main drive for a new world. I've made a chapter by chapter summary for my blog.