It revolves around the characters Marie-Laure LeBlanc, a blind French girl who takes refuge in her great-uncle's house in Saint-Malo after Paris is invaded by Nazi Germany, and Werner Pfennig, a bright German boy who is accepted into a military school because of his skills in radio technology.

Doerr spent ten years writing All the Light We Cannot See, with much time dedicated to research on World War II.

When Nazi Germany invades France in 1940, Marie-Laure and Daniel flee to the coastal town of Saint-Malo to take refuge with her great-uncle Etienne, a reclusive, shell-shocked veteran of World War I who spends his time broadcasting educational audio recordings, produced by his deceased brother, across Europe.

Unbeknown to Marie-Laure, the museum has entrusted her father with either the Sea of Flames or one of three exact copies that were made to protect the original gem.

Eventually, while Marie-Laure is going home to deliver a routine Resistance message from the bakery, she is visited by Sergeant Major Reinhold von Rumpel, a Nazi gemologist who is searching for the Sea of Flames and has tracked the real one to Saint-Malo.

He discovers this skill in 1934 at the age of eight after he finds a broken radio with his sister Jutta, fixes it, and uses it to hear science and music programs transmitted across Europe.

In 1940, Werner's skill earns him a place at the National Political Institute of Education at Schulpforta, a draconian state boarding school teaching Nazi values, which Jutta hates.

After enduring bullying, Frederick suffers a severe beating at the hands of his fellow students, leaving him with permanent brain damage and forcing his return to his home in Berlin.

Using Etienne's transmitter, she tries to call for help by transmitting herself reading a braille version of the science fiction novel Twenty Thousand Leagues Under the Seas alongside pleas for rescue.

Thirty years later, Volkheimer finds Jutta, who is now a married math teacher, and gives her Werner's belongings at the time of his death, including the model house that contained the Sea of Flames.

Jutta travels to France with her son Max to investigate the model and meets Marie-Laure in Paris; she is now working as a marine biologist at the Museum of Natural History.

[7][9][13]: 6:54–7:18  Doerr became interested in how, in his words, "a place could so thoroughly hide its own incineration": that the city felt ancient to him, in spite of its destruction near the end of World War II.

[14] He formulated his scene to have the boy trapped somewhere in Saint-Malo and listening to the girl reading Jules Verne's Twenty Thousand Leagues Under the Seas over the radio.

[7][4] Doerr read diaries and letters written during World War II and visited Germany, Paris, and Saint-Malo for further study.

Despite this, his research allowed Doerr to add historical details to his narrative, including speech transcripts and the names of German radio manufacturers.

[19] Germany's attempt to acquire all of Europe leads to its downfall, as von Rumpel tries to retrieve the cursed Sea of Flames, highlighting the dangers of greed.

Another theme is the nature of sacrifice; Daniel gives the Sea of Flames to Marie-Laure to keep her alive despite the curse leading to his arrest, and Werner is forced to risk his life for Germany.

Despite his sympathetic portrayal, the narrative does not excuse his actions in the military and increasing tolerance of violence, though he ultimately finds redemption when he rescues Marie-Laure.

[8] Particularly, through the symbolism of the Sea of Flames and its legend, All the Light We Cannot See illustrates how pursuing human desires can lead to war and misery.

[27] All the Light We Cannot See also re-creates the deprived conditions of France during World War II and the strict lives of the occupying German soldiers.

[9] Christine Pivovar of the Kansas City Star stated, "Science and the natural world [in All the Light We Cannot See] take on the role of the supernatural in a traditional fairy tale.

According to Cha, the invisibility of most of the electromagnetic spectrum is a common motif throughout the book, and imparts "texture and rhythm as well as a thematic tension, between the insignificant and miraculous natures of mankind and all the immeasurable components that make up our lives".

[23] When the story reaches the early 21st century, a character contemplates the abundance of electromagnetic waves flowing from cell phones and computers,[25] wondering if souls could be traveling between them.

[32][38] Anthony Doerr found the novel's popularity unexpected due to it featuring a sympathetic Nazi and containing intricate passages about technology.

[53][5] In a starred review for Booklist, Brad Hopper called it "a novel to live in, learn from, and feel bereft over when the last page is turned".

This has been acknowledged by the book author who remarked that he found himself "for years trying to justify that [ending] through historical accuracy, to say it wasn't very likely that Werner would have more than a few minutes.

[17] Both Green and Justin Cartwright expressed concern about All the Light We Cannot See portraying the Nazis and the Allies in war as falsely morally equivalent.

[27][58] In March 2019, Netflix and 21 Laps Entertainment acquired the rights to develop a limited television adaptation of All the Light We Cannot See, with Shawn Levy, Dan Levine, and Josh Barry as executive producers.

[61] With approval from Doerr, Levy removed potentially upsetting scenes late in the story for the adaptation, stating that he wanted the ending to feel optimistic.

[63] The Hollywood Reporter's Daniel Fienberg specifically thought that by the third episode, the plot barely resembled the novel, with each change making the "material louder, clumsier and less emotionally rich.