Ah, there's the Calvino I was expecting. This is pure fantasy -- a viscount split into halves by a point-blank cannonball, each half going on to live their life of progressively-worse evil or progressively more righteous goodness.

The story before the good half (ironically, the sinistro or left side) shades into horror, as the bad half roams about his domain slicing flowers and small animals into halves -- but once the good half appears, it becomes more of a cautionary tale about the necessity of balance. Both the Huguenots and the lepers come to dread the good half's appearance as much or more than the bad half's visits.

I don't think this is an incredibly deep story, but I do think there's something to be mined from the inventor -- especially the difficulty he had creating the visions of the good half, compared to the ease with which he created instruments of torture for the bad, and his pride in his craft regardless of the purpose to which it had been put.

Regardless of all that: it has the evocative flair that Calvino started developing in his earlier short stories, and it's the first true exploration of what laws and constraints of reality he could abandon to tell the story he wanted to.

Oh! And we have another appearance of a mass of ants.