The book is made of nine chapters, each telling a different story, not in chronological orderer.
The first story tells us about Yunior, the main character in the book. He lives with his brother Rafa and his mother in a small house. They are immigrants from the Dominican Republic and came to the US when Yunior and Rafa were kids. At the beginning of the story, Yunior has a girlfriend, Magda. He cheats on her with another girl, Cassandra, but unluckily for him, Cassandra writes a letter to Magda, telling her about everything that happened between her and Yunior. Magda doesn't want to see him anymore, but after weeks of begging, crying and calling her every night, Yunior manages to get back with her again. However, things aren't the same anymore. Magda is distant to him now. She starts dressing better, cuts her hair, goes out on Friday nights to dance with her friends. These things make Yunior even more fearful that he might lose her, so he decides to go on a trip with her in the Dominican Republic. She is hesitant at the beginning, but then she decides to go with him. Things don't change though. Magna grows even more distant to Yunior, and he senses that something is really wrong. After some more days at the resort where they are staying, Magna finally tells him that she doesn't want to stay there with him anymore and that she is leaving the next day.
The second story is mostly about his brother Rafa and his girlfriend, Nilda. She is Yunior's friend at the beginning. She stays a lot at his apartment because she hates staying at her house with her mother. One day Rafa comes home and he sees Nilda. Rafa is muscular, handsome and has a good reputation with girls, and Nilda falls over him. Yunior doesn't want her to become Rafa's girlfriend; he thinks his brother will mistreat her and cheat on her. The next day, however, Rafa kisses her and she becomes his girlfriend. From then on, she comes to their house almost every night, sleeps with Rafa in the same room where Yunior sleeps, and then early in the morning leaves so their mother won't find out about her. Later Rafa is diagnosed with cancer and the story goes on and tells what happens with Nilda after Rafa's death.
The third story is about Yunior and his girlfriend, Alma. She loves him and she does everything for him. They are very different from each other; she is slender, he is bulky and muscular, she likes to drink, he likes to read; they are the opposite of each other and Yunior explains their love as being an opposites-attract sort of thing. She is very playful and adventurous in bed, and Yunior appreciates her for that. However, one day, she opens his notebook and finds out that he is cheating her. When asked about it, Yunior says that what is written in the notebook isn't real; is just part of a novel he is writing. She doesn't believe him and leaves.
The fourth story in the book is the only one which doesn't talk about Yunior. It is about a Dominican immigrant girl named Yasmin. She comes when she is young in the US and lives in a house with many other girls. She doesn't like her new life, her new house where girls often steal and fight with each other, her new job where she does laundry. Eventually, she finds a boyfriend, Ramon, who is a married man. His family lives in the Dominican Republic and he often writes letters to them. Ramon dreams about buying a house, and finally, he and Yasmin find one. They end up buying it and Ramon is very happy. He is constantly working on the house to fix broken things and is proud of himself because not many immigrants are capable of buying their own houses. Still, both of them aren't satisfied with their lives. They are constantly looking for more and miss their old lives in the Dominican Republic.
The fifth story tells us about Yunior and his girlfriend, Flaca. They meet together at school and at the beginning Flaca doesn't want to be in a relationship with him. However, after sometimes, she ends up with him. Flaca is white, and this is the reason why she is disliked by Yunior friends. They don't want her to stay with him in his house when they are around so she always leaves when they come. She is different from Yunior's other girlfriends too; she likes to read books and accompanies him to the bookstore. They both know that they relationship will not last forever, that one day they will both leave and continue with their own lives. However, they are both afraid to continue with their own lives. Eventually, one-day Flaca leaves and they never talk to each other again.
The sixth story talks about Rafa after he discovers he has cancer. Weakened by the disease, he spends months in the hospital. After being recovered, he starts a legitimate job in order to feel helpful again. Unfortunately, his cancer returns and he becomes sick again. He meets a girl, Pura who has come to the US illegally and wants to marry him to get citizenship. Rafa's mother is against this, even Yunior tells his brother that she is staying with him only to get the papers. Despite all of this, Rafa marries her. His mother is so furious that she tells him to leave her house and never come back again. He does come back though, to steal money from her. She knows about this but still allows him. Rafa gets sick again and has to go to the hospital. While he stays there, Pura never comes to visit him. She meets his mother one last time and asks her to give her some money, and then disappears. Rafa comes home again and he never sees Pura again.
The seventh story talks about the young Yunior and Rafa, and how they come with their mother in the US. They meet their father for the first time in they life and discover the harsh reality that will face them from now on. They don't speak English and their mother makes them see TV all day so they can learn the language from TV shows. They aren't allowed to go out because it is too cold and because their father thinks it is not suitable for them to go out yet. However, Yunior gets bored and often goes out without permission and even makes some American friends. They all get bored with the life in the US and wish to go back to the Dominican Republic, especially their mother. She finds it especially hard because she has no friends and doesn't know the language. Finally, during a snowstorm, she takes her kids and they go out together and explore the neighborhood.
The eighth story describes how Yunior feels after his brother's death. He thinks that his life is over now too and that he doesn't have a purpose in life. He sees apocalyptic dreams and is very depressed. The only person who seems to listen to him is his neighbor, Miss Lora. She is too old for him and he has a girlfriend, but still, he falls for her and they end up dating each other for some years. Finally, Yunior moves on and leaves her. Later he tries to find her again but is unsuccessful in doing so.
The ninth story tells about Yunior's adult life over the course of five years. He breaks up with his fiancee because she discovers him cheating on her. He then spends years in depression, trying to forget her with other girls, jumping from one relationship to the other, without success. He even leaves a girl pregnant, but after she reads that he is writing bad things about her in his journal, she leaves. Yunior moves to Boston but finds it hard to adjust to life there because people are racist towards him and often say racist things when he passes nearby. He finally learns that he will never totally forget his fiancee who left him and decides to write a book about all of his failed relationships.
