I can absolutely see some of the path between The Path to the Nest of Spiders and Calvino's later works. The first ... half, maybe? ... of the stories are sketches, almost devoid of plot, but incredibly well-drawn images of the less well-off towns of Italy in the mid-20th century. Once we hit "Animal Woods," though, we're in full-on fairy tale mode, and "Theft in a Pastry Shop" continues it; the latter half of the stories drift in a more fantastic direction, though not as far as Calvino will go in the next Year of Calvino read (The Cloven Viscount).

Theme-wise: Calvino has yet to write a female character as an actual character; women and girls are fully props most of the time -- see "Sleeping like Dogs" and "The Adventure of a Soldier" for instances where they're actually props.

And, even in the early stories, there's both a focus on ants (prefiguring The Argentine Ant, maybe) and on bounty, on large masses of ... animals (ants), plants, etc.

I think Calvino might be interested in exploring class, but it's pretty backgrounded in most of the stories -- overshadowed by people struggling in the aftermath of the war. There are a few stories focused on more powerful members of society, and they're entirely in the wrong ("The Master's Eye" and "A Judge Is Hanged", for instance.)