We are in Trieste between the late nineteenth century and the early years of the twentieth.
The author imagines that a psychoanalyst publishes "out of revenge" the memoirs of one of his patients, who broke off treatment and told a pack of lies.
The novel thus adopts the narrative form of an autobiography.
"Lying comfortably in a club armchair," Zeno attempts to recall the most significant events of his existence, mindful that

the most intense life is recounted in synthesis by the most rudimentary sound, that of the sea wave, which, from the moment it forms, changes at every instant until it dies

.
The effort to return to the past is not a chronological journey, but rather a lingering over the crucial moments of life.
Indeed, the narrative structure follows the shifting viewpoints from which Zeno observes his own biography.
The first chapter centers on smoking—or rather, the last cigarette, that perpetually broken resolution to abandon the habit.
The reader immediately encounters the subtle, paradoxical irony that permeates the entire book, but also confronts the novel's central theme: the dread that

finding myself racing through time, I could no longer be reached by love

and, more broadly, by what one would wish to be.
Returning to the past resurrects the chasm between one's aspirations and what has been attained.
A persistent sense of guilt emerges, for which a plausible justification must be found.
The awareness of having "lived in vain," as Leopardi put it, "shall embitter me," feeding a mixture of melancholy and anguish.
Remembrance is

sweet in itself; but painfully the thought of the present intrudes, an idle yearning for the past, sorrowful though it was, and the saying: I was

(Le ricordanze).
The subsequent chapters develop the same theme within an increasingly complex and articulated narrative framework.
Zeno investigates his own psyche in relation to the primary figures of his life.
In the second chapter, "death of the father," Zeno is unable to offer the filial affection he desires because his father’s disappointment over his son’s blatant ineptitude as a businessman is too profound.
In the third chapter, "marriage," the protagonist fails to attain love, embodied by the beautiful Ada, and marries—without knowing why—Augusta, the plain sister.
In the fourth chapter, "wife and mistress," Zeno is neither a good husband nor a good lover, while in the fifth chapter, "partnership," it is friendship that is lost.
Zeno, who nevertheless tried in every way to help Guido, Ada’s husband, proves incapable of averting his financial ruin and suicide, to the extent of being accused by Ada, his eternal love, of having betrayed his friend.
The autobiography could well conclude at this point.
Instead, the doctor’s assertion that Zeno is cured—because he has realized that in his unconscious he loved his mother and hated his father (the famous Oedipal dynamic)—triggers a rationalistic reaction from Zeno, who candidly confesses that he has lied all along, readily offering a justification:

(the doctor) studied nothing but medicine and therefore does not know what it means to write in Italian for those of us who speak, but do not know how to write in, dialect....
if he only knew how we favor recounting all those things for which we have a phrase at hand, and how we shun those that would force us to consult a dictionary

In truth, if we adopt an outside perspective rather than Zeno’s, events could be interpreted quite differently from the protagonist’s view.
Zeno is a good son who strives to remain close to his father; he is a good husband despite a few dalliances; he cares for his children; he is generous, ready to help his mistress and a friend in distress; he even reveals himself to be an astute businessman when forced to be one.
All his existential dilemmas arise from how he experiences life within his consciousness rather than from actual lived reality.
It will take the war to tear away the veil of ignorance Zeno harbors about his own life and to reveal that the protagonist can face adversity and even turn it to financial advantage.

Is the book, then, merely facile irony directed at psychoanalysis, and more broadly at psychology?—disciplines that seem intent on contriving problems where a rationalistic approach to life would offer a workable, serene solution.
In reality, the novel can be read in concentric circles, moving from external reality to the unconscious and vice versa: the depiction of the deep self’s impact on human consciousness, a true exception to the prose of existence.
There exists an interpretive key to every consciousness, which the author must concede, his rationalistic approach notwithstanding.
For Zeno, this interpretive key seems to reside in the good–bad dichotomy, nurtured by an episode from his childhood.

I watched without great pain the torture inflicted upon Guido by the balance sheet I had drawn up with such care, and a curious doubt came over me, followed immediately by a most curious memory.
the doubt: was I good or bad?...
I saw myself as a child, dressed (I am certain of it) still in short skirts, looking up to ask my smiling mother: am I good or bad?....
Oh, incomparable originality of life! How wondrous that the doubt it had once inflicted on the child in so childish a form had not been resolved by the adult who had already marked the midpoint of his life

Why read it? It is a remarkably dense, complex book, brimming with insights.
It must be read, though not before falling asleep.

Zeno's Conscience