This work describes the French coal mines around 1860 to 1865.  Zola is looking at the start of the union movement and the early growing pains of those trying to improve their working conditions.  As always Zola's attention to the sights and sounds of the pit makes the work worth the read.  Also the examination of how those who are downtrodden rise up and, in this case loose, to the moneyed bourgeoisie class.  Those described as living a life of leisure on the backs of the working man.  Could inspire this post covid generation of workers to take what is theirs by the sweat of their brow and burn down the bourgeoisie and their life of fat.