Georges Simenon lived on a boat for a while, and spent a lot of time travelling through the French canal system. So he was probably grinning at the idea of setting a novel in this environment, with Maigret looking “to absorb the atmosphere, to capture the essence of canal life, which was so different from the world he knew.”
Personally, I don’t know a thing about canal life. I have a general idea of how canals and lock systems operate, but that’s it. This made my ability to visualize some of the action in this one difficult, making me think of Peter Mendelsund’s book What We See When We Read (short answer: we make most of it up).
Canal life, however, is just window dressing here. The story follows what I guess, having read a few of these now, is the usual script. There is the juxtaposition of high life and low, with the yacht Southern Cross and the barge Providence representing different ends of the social-economic (but not moral) divide. There is the man, and in this case a woman too, leading a kind of double life, which requires Maigret to dig into their past. And finally the killer is revealed as someone we have sympathy for, their crime the last stop in a life lived downhill, full of disappointment and despair.
A good read, but the plot is based on a pile of improbabilities and coincidences. This is also par for the course. Maigret himself never seems to do much actual detective work aside from tracking a few leads to nail things down at the end. Instead, a wall cracks and the killers sort of crumble on their own.