It tells the story of a troubled man incapable of revealing his true self to others, and who, instead, maintains a façade of hollow jocularity, later turning to a life of alcoholism and drug abuse before his final disappearance.

[4] It enjoys considerable popularity among younger readers[5] and ranks as the second best-selling novel by publishing house Shinchōsha, behind Sōseki Natsume's Kokoro.

As time goes on, Ōba becomes increasingly concerned over the potential exposure of his imitative cheerful façade when his schoolmate Takeichi sees through one of his false buffoonery.

During this time, he meets a single mother who is an acquaintance of Horiki and tries to have a normal relationship with her, serving as a surrogate father to her little girl, but soon, he returns to his drinking habits and his fear of humanity; he eventually abandons them.

The terror and despair brought on by this incident estranges Ōba from his wife and leads him to another suicide attempt with soporific drugs.

He is confined to a mental institution and, upon release, moves to an isolated place with his brother's help, concluding the story with the comment that he feels neither happy nor unhappy now.

The novel presents recurring themes in the author's life, including suicide, social alienation, addiction and depression.

[10] Despite his inability to belong to the in-group, Ōba recognized that favoritism must inevitably exist among human beings and they will show a form of negative bias towards members of the out-group.

[12] His refusal to change the state of his social identity is in contradiction to the theory that individuals will attempt to improve their self-confidence if threatened.

This caused further disconnect from others and alienation from himself, like a clown who appeared happy on the outside, but was unable to find peace inside himself anymore.

He was deeply influenced by Uchimura Kanzō, whose teachings were grounded in the Calvinistic tradition and preached a puritanical worldview that centered on the image of a strict Christian God.

The image of an unforgiving and irate God, the existence of hell and predetermination were reinforced by Dazai’s sense of guilt at the death of Tanabe Shimeko, with whom he had attempted a double suicide, as well as by personal setbacks in his failure to secure an important position with a major newspaper and the fact that he had not been selected for the Akutagawa Prize at the time.

This theme appeared towards the end of No Longer Human, in a dialectical diatribe between the protagonist and the Almighty, during which Oba ask whether trustfulness is a sin.

He also pointed out that the "blunt" style distanced the book from the tone of an actual autobiography, despite the similarities to Dazai's own personal life.

[20] Serdar Yegulalp of Genji Press noted (in 2007) the strength of Dazai in portraying the situation of the protagonist, describing the novel as "bleak in a way that is both extreme and yet also strangely unforced".

[21] One modern analyst, Naoko Miyaji, has proposed Dazai was suffering from complex post-traumatic stress disorder when he wrote the book.

[23] The novel received another English translation in 2018 by Mark Gibeau as A Shameful Life, published by Stone Bridge Press.