I read this book many decades ago, in French original. A few years later, I saw the movie (most probably with the same title) that was made about it, also in French. I'm positive the author is French and originates from Southern France.
The action is in a small village in southern France, many decades ago, I'd guess early 20th century. Most probably in Provence but there are places in Languedoc that might fit.
It begins when an old man, in what will eventually be his deathbed, starts to mumble meaningless words. I remember perfectly the verb used to describe that : "déparler" which is totally obsolete now. But the meaning is easy to guess. "Parler" means "to speak", so "déparler" is to speak in an incorrect way, a bad way, possibly to curse.
And indeed the other villagers suspect that his mumbling might be curses, because a succession of disasters hit the village: drought, fires, death of animals....
One might consider it is "out of topic" because, independently, none of the events is abnormal per se. Only the succession is strange.
The entire atmosphere of the book, however, follows the superstition of the villagers who are convinced that the old man brought them this curse, but they fear to kill him. And indeed, when he finally dies a natural way, everything returns to normalcy.
More details : formally the head of the village is a man, but in fact most of the important decisions are made by a middle-aged woman with an extremely strong personality. Possibly a widow, or perhaps never married, but certainly without a husband at the time of the events.
There is also the "idiot du village", unable to do a real job. I'm not sure he can help at all, but at that time no village would let his "idiot" starve. At some point of book (and the movie), one realises that the "strong" woman has regular sexual intercourse with him. IIRC, he dies in a fire that destroys a building (abarn ?), and she cries with a sincere sorrow.
