Described as a conte philosophique[1] and a metaphor for independence, it tells the adventures of a boy who climbs up a tree to spend the rest of his life inhabiting an arboreal kingdom.
Set in an imaginary village on the Ligurian Riviera, Ombrosa represents the author's vision as a central theme, little inclined to judgments and dull opinions.
The novel is narrated by Biagio, the younger brother of the protagonist, and is the story of a young baron, Cosimo Piovasco di Rondò, firstborn of a noble family sadly behind the times.
Its end comes about in an unusual way: aged and sick, feeling the onset of death, Cosimo climbs to the top of a large walnut tree and hangs himself on a passing balloon.
[1] Despite these perceived flaws, critic Martin McLaughlin argues that the novel "remains something of a tour de force in Calvino's oeuvre.