The novel opens with the protagonist reflecting on her obsession with the enigmatic 'man I want to be with.' She describes him as a cultural force, intelligent, and well-respected, making her feel a sense of power in his presence. However, her infatuation is tainted by the knowledge that he is married. She acknowledges her fear of becoming a cheater and making her boyfriend an unwilling accomplice. Life continues for the protagonist as she observes her parents, who go on a group holiday to India despite not staying with their South Asian relatives, leading to humorous misunderstandings with their white fellow travelers. Despite these cultural clashes, the protagonist's mother enjoys the trip and forms new friendships.

The protagonist's daily routine involves walking her dog, Mocha, in the park near Djuna and Milo. Djuna, a woman she encounters regularly, piques her interest, leading to friendly interactions and a growing connection. Meanwhile, the 'woman I am obsessed with' undergoes a major life change, breaking up with her long-term boyfriend and moving to Marfa, Texas, to open a café. The protagonist finds solace in her misfortune, believing that she now has a chance to own a home. This desire is driven by her own financial instability, contrasting with the financial security enjoyed by the 'man I want to be with' and his wife.

The protagonist's insecurities are further exacerbated when the man mentions lying in bed with the woman she's obsessed with, naming their future children together. This revelation disturbs the protagonist, making her confront the dissonance between the man's public image of caring about social justice and his private behavior of being careless and craving more love and attention. As the protagonist witnesses the woman she's obsessed with building her new life in Marfa, her anxieties intensify. She even becomes jealous when the man showers affection on a dog, highlighting the skewed nature of her relationship with him.

Gradually, the protagonist and Djuna become closer through their park encounters. The protagonist makes an effort to be a good listener, reflecting Djuna's positive qualities back to her. Their friendship deepens when Djuna mentions her half-sister, who happens to be the woman the protagonist is obsessed with. Desperate to get closer to the man she desires, the protagonist attempts to surprise him at an event but is met with shock and anger when she discovers his wife is present. This experience only humiliates her further.

The protagonist develops a strong aversion to the man's wife, labeling her as an untalented artist who is not the main character in anything, even her own life. She takes a subversive action by writing "fuck you" underneath the wife's artwork in a gallery, venting her frustration. As the woman she's obsessed with gains social clout and popularity on social media, the protagonist becomes increasingly envious, feeling like she's lost her relevance in the online world. She contemplates applying for a job as her personal assistant to gain proximity to her idol but ultimately decides against it, unsure of what she would do next.

In the final vignette, the man suddenly contacts the protagonist, proposing a sexual encounter after three years of no contact. The protagonist eagerly agrees, fantasizing about becoming pregnant by him and exerting power and possession over him. The novel concludes with this tantalizing prospect. I'm a Fan is a complex exploration of obsession, insecurity, and the pursuit of unattainable desires. Through a fragmented narrative, Sheena Patel invites readers to delve into the intricacies of modern relationships and the ways in which identity, social media, and ambition shape our lives.