My first IF in French. (I'm not counting Les Heures du Vent because it was unfinished and I quit.) I can read French quite well, but it took some time (and some help from online dictionaries) to figure out the commands.
Catapole is very, very well written. You play as a chimneysweep in a huge underground complex, where workers live and work their entire lives to support the wealthy who still live on the surface. This underground atmosphere, the stillness of the air, the soot,... is made tangible by the writing. It is also reflected by the PC, with his mood, his views on life underground. Not really unhappy, but aware that there is much of the world that lies beyond his grasp.
Because of this surrender to the status quo, he becomes the target of a murder attempt by revolutionaries who want to shake the public into a revolt against their living conditions. Up to you, the player, to find the way to survive this attempt and choose a way of life for your PC.
These are deep themes, thought-provoking and worth contemplating. Unfortunately, the game does not do them justice.
However well-written, Catapole is too short to get in-charachter, too on-rails to understand the life underground, too confined to get a grasp of the relation of your PC to his world and to the people he lives with.
The same is true for the motives and the actions of the revolutionaries.
There's just not enough immersion in the grand overarching story to understand the main character and to make a valid choice at the end.
Still, Catapole is well worth a playthrough for the exquisite writing, and to let yourself wonder about the options.