As an example, there's an entire chapter dedicated to Michel and his professor friend going through a long list of nineteenth-century authors and passing judgment on them. You would expect this to be the thinly disguised opinions of Jules Verne, but no, it's the thinly disguised opinions of Verne's editor, which Verne included in the hopes that it would help the book get published. Obviously, this was not successful.
I have a theory about Verne that's strongly based on this book. He is sometimes called a technological visionary, but most of the inventions of his books were already known at his time (the first submarine was made in 1620, Around the World in Eighty Days is likely based on an itinerary in a magazine Verne read, etc.), and what was not known, Verne often made work using lots of artistic license (like the giant gun from the Earth to the Moon, which would kill the passengers with the acceleration; Verne did not invent rockets). No, Verne's genius was that he took the progress that was already visible and used it to create adventures, that he created a vision of the future where all this technology is used to explore deep underground caves and the sea floor and outer space and find fascinating things there. And Paris in the Twentieth Century is the negative version of this, a world where technological progress does not expand imagination, but instead limits it, as everything gets economically optimised to death. It's a good warning to keep in mind.