The novel, using three narrative voices, details the rise and fall of Hasan, a young Muslim who is raised to be religious but winds up doubting his faith after dealings with his Marxist–Leninist childhood friend and an anarcho-nihilist writer.

Mihardja, a journalist-cum-literary editor who associated with the eccentric poet Chairil Anwar and the Socialist Party of Indonesia, wrote Atheis from May 1948 to February 1949.

Although the writer insisted that the work was meant to be realistic, symbolic representations from subjective meanings to the novel being an allegory have been advanced.

Religious thinkers, Marxist-Leninists, and anarchists decried the novel for not explaining their ideologies in more detail, but literary figures and many in the general public praised it; this positive reception may have been influenced by the nascent government's need to promote literature for nation-building.

However, Rukmini, who is from a higher social class than him, is set to marry a rich man from Batavia (modern day Jakarta).

In Bandung, Hasan works for the Japanese occupation government and lives an ascetic lifestyle, often fasting for days on end and dunking himself into a river to refresh his body between evening and morning prayers.

Soon Hasan becomes increasingly divorced from his religious upbringing, at one time skipping the mandatory maghrib prayer to watch a movie with Kartini.

Through Rusli, Hasan is introduced to people from different ideologies, including the anarcho-nihilist playboy Anwar; he also begins courting Kartini.

Eventually, Hasan sees Kartini and Anwar leaving a hotel near the train station and incorrectly assumes that she had been cheating on him.

Not long afterwards, Hasan goes out into the night after curfew and is shot in the chest by Japanese patrols, dying after torture at the station with the Islamic creed "Allahu Akbar" on his lips.

Mihardja, who was born and raised in Garut, West Java, was trained as a journalist[12] before moving to Batavia in 1941 to work for the state publisher of the Dutch East Indies, Balai Pustaka.

[13] Atheis was Mihardja's first novel; what few literary works he had written beforehand were mostly short stories and dramas, both those intended for the radio and the stage.

[16] Meanwhile, emerging writers such as Idrus, Asrul Sani, and Chairil Anwar were increasingly critical of the older generation of Indonesian authors, whom they decried as narrow-minded and provincial.

[1][11] The novel starts with a third-person description of Rusli and Kartini's visit to the Japanese police headquarters after hearing of Hasan's death.

Afterwards, the narrator, referred to only as "saya", describes in the first person how he met Hasan and how the main character came to tell him his life's story.

Teeuw describes the diction as forced in places, with sentence structure deviating from those used by the Minang writers who dominated that period's Indonesian literature.

[20] Maier notes that the novel features "odd but appropriate metaphors and similes" and stylistically resembles earlier works such as Abdul Muis' Salah Asuhan (Wrong Upbringing; 1928), Sutan Takdir Alisjahbana's Layar Terkembang (With Sails Unfurled; 1936), and Armijn Pane's Belenggu (Shackles; 1940).

[8] Balfas also notes stylistic similarities with older works, such as the death of the protagonist at the climax,[5] and Sastrowardoyo opines that Belenggu had a more modern styling despite being published nine years earlier.

[13] Maier notes that the fame and warm reception to which Atheis was released was influenced not only by the novel's strengths, but also by Mihardja's personality and stature.

[32] However, other readers – many from the literary community – praised the novel, including writers Pramoedya Ananta Toer and Haji Abdul Malik Karim Amrullah.

[40][14] At the launch of Manifesto Khalifatullah, a religious-themed novel, Mihardja stated that it was "the answer to Atheis", after he came to believe that "God made man to be His representative on earth, not that of Satan".