The novel If on a winter's night a traveler is comprised of twelve numbered "frame story" chapters and ten named story-within-a-story chapters. Most of the numbered chapters are narrated in the second-person point of view, meaning it is told as if "you" were the protagonist. Some of the stories-within-a-story are also metaliterary, but many of them are told in more traditional first- and third-person point of view.
The frame story begins with "you," the reader, going to the store to buy Italo Calvino's new book, If on a winter's night a traveler. The reader obtains the book and begins to read. The story is about a man in a train station who is on a mission to exchange a suitcase with someone. The reader soon finds that the book was incorrectly bound so that the same signature, or group of pages, is repeated over and over. The reader returns to the bookshop to exchange the book and finds that the book he was reading was not by Calvino at all. He gets what he thinks is a full copy of the book he was reading, called Outside the town of Malbork. He also meets another reader named Ludmilla, who was given a copy of Calvino's book with the same problem. They exchange phone numbers.
When the reader begins reading Outside the town of Malbork, he finds it is not the same story he was reading before. It is about a boy living in a place called Kudgiwa, trading places with another boy so that they can learn different trades. The character feels great consternation at being replaced and jealousy at the thought that the other boy could strike up a relationship with a girl he likes. This book turns out to have another binding error; the book has many blank pages and abruptly switches stories just as it is getting interesting.
The reader looks up where the story takes place and finds out the towns in the story are from a country called Cimmeria. He calls Ludmilla and tells her they should meet, and she suggests they meet with a professor named Professor Uzzi-Tuzii who is an expert on Cimmerian literature. When the reader arrives at the university, he is directed to Professor Uzzi-Tuzii's office by a young man named Irnerio. Ludmilla is not there, so Professor Uzzi-Tuzii lectures the reader on Cimmerian language and literature; then he begins reading a story he thinks is the same one the reader was reading. This story, Leaning from the steep slope, has the same names of places and people but is an entirely different story. In the story, a paranoid man living at a hotel becomes involved in a plot to free a prisoner.
When Professor Uzzi-Tuzii stops reading, the reader realizes that Ludmilla has appeared. Her sister, Lotaria, also visits the office of the professor and invites the reader and Ludmilla to a seminar. They attend, and the story read in the seminar is again completely different from the others. In this story, named Without fear of wind or vertigo, a man becomes friends with another young man and a young woman during a war. They eventually join in a three-person sexual relationship. Then, during a session of lovemaking, the main character finds a government document calling for him to be killed. The story breaks off, and the students in Lotaria's seminar begin to analyze it through certain academic lenses. The reader and Ludmilla are more concerned with finishing the story, so they leave together to talk at a cafe. They decide that the reader will go to the publishing house to clarify what the problem is.
At the publishing house, the reader meets a man named Mr. Cavedagna. The man tells him that the trouble has stemmed from a scheming translator named Ermes Marana. Mr. Cavedagna gives the reader the manuscript of a new book called Looks down in the gathering shadow. In this book, a man and woman try to get rid of the body of a dead man without being found out. When the reader reaches the end of the manuscript he's been given, he wants to read more, but Mr. Cavedagna says that the rest has been misplaced. He lets the reader read a series of confusing letters from the translator, Ermes Marana, which span his travels around the globe interacting with secret literary organizations. When the reader leaves the publishing house, Mr. Cavedagna lets him take a manuscript of a story called In a network of lines that enlace.
The reader arrives at the cafe to meet Ludmilla again and begins to read In a network of lines that enlace. The text centers on a man who, while on a run, wants desperately to answer a phone that he hears ringing inside a house. When he does answer the phone, he finds out that one of his university students is going to be murdered if he doesn't stop it. He is able to stop the murder, but the student is not grateful. The reader is interrupted by a call from Ludmilla asking to meet at her house instead. The reader goes to her house and snoops around, judging her character based on her apartment's contents. Irnerio arrives at the apartment, and his casual manner makes the reader jealous about his relationship with Ludmilla. Irnerio shows the reader a typewriter and reveals that that Marana was once involved with Ludmilla. Ludmilla arrives and Irnerio leaves. Ludmilla and the reader have sex. When they are lying in bed together afterwards, the reader begins to tell her about the manuscript he took from the publishing house. When he goes to the other room to retrieve it, he finds that Irnerio has taken it, but there is another book that looks almost identical.
The reader begins to read this book, which is called In a network of lines that intersect. In this book, a man obsessed with mirrors becomes so concerned about being targeted that he arranges for multiple versions of everything in his life, including cars, businesses, his mistress, and himself (using body doubles). He tries to organize a fake kidnapping to foil a real kidnapping he thinks will take place, but he is successfully kidnapped. Instead of returning to the frame story after this novel excerpt, the narrative turns to the journal of Silas Flannery, a writer of popular novels. He has a bad case of writer's block and spends much of his time every day looking out the window at a woman reading. Throughout this chapter, it becomes clear that the woman is Ludmilla, and both she and Lotaria appear in Flannery's life to discuss their views on literature. Flannery also meets a group of scouts who think aliens are trying to communicate through Flannery. Flannery is also involved with Marana, who tells him about fake translations of Flannery's works in Japan. At the end of the chapter, Flannery meets the reader and gives him a translation of a Japanese book, lying that it is the same book he was reading previously.
The Japanese story, On the carpet of leaves illuminated by the moon, tells the story of a young man who becomes sexually involved with the wife and daughter of his boss. The reader reads this book while on an airplane and upon arriving at his destination, a country called Ataguitania, the book is taken from him. The reader is taken on a confusing journey with a woman who changes names and identities repeatedly. He and the woman, who may in fact by Ludmilla's sister Lotaria, eventually have sex in a room where the book Around an empty grave is being printed. After having sex, the reader begins to read the story. In the story, a young man seeks to find his mother and learn about his father's past. He finds out that his father impregnated an Indian woman before dueling with and killing her brother. Just before the narrator himself seems about to enter a duel to the death, the story is cut off.
The reader is taken to a jail run by undercover revolutionaries and soon after is sent on a mission to liaise with the Director General of the State Police Archives of Ircania about the banned books in Ataguitania and Ircania. They discuss book-banning, Marana's translations, and a book called What story down there awaits its end?, which is supposedly the same story as Around an empty grave but set in Ircania. The reader meets a man to receive the book What story down there awaits its end? but is only able to get part of the book before the man is ambushed. The story describes a man who walks the streets of a city making people and buildings disappear. When he is confronted by men who thank him for making everything disappear, he tries to get everything to come back and realizes that he can't. He sees the woman he loves in the distance and runs to her as the blank plane around him cracks apart.
The reader returns from his travels and tries to check full versions of the stories he's been reading out from the library. While he waits for the librarians to find the books, he gets into a conversation with a group of men about the different ways they enjoy reading books. The librarians tell him that all of the books he has requested are unavailable.
The narrative skips suddenly to the reader and Ludmilla in bed together, reading and preparing to sleep. Ludmilla tells him to put his book away and the reader responds that he is almost done with Calvino's book.
