If I Stay is a short novel by author Gayle Forman. The story follows one day in the life of seventeen-year-old Mia, who has been critically injured in an accident that took the lives of her parents and younger brother. As Mia has an out-of-body experience that enables her to observe all that is happening around her, she reflects on her. She is faced with the decision of whether she wants to fight to live or let go.

When the novel opens, an inch of snow has fallen overnight. Schools in Mia's Oregon hometown are closed for the day. Mia, her father (who is a middle school English teacher), and her younger brother Teddy are home for the day. Her mother takes the day off from work, and the family sets out on a day trip. Mia, a serious cellist and classical music lover, is blissfully listening to a sonata when a truck hits the family's car, killing her parents immediately and seriously injuring Mia and Teddy. Immediately following the accident, she is unconscious from a traumatic head injury, Mia begins having an out-of-body experience through which she is able to observe herself and everything around her without feeling pain. Initially, she believes that she is dead.

Mia and Teddy are rushed to a local hospital. Then, Mia is flown to a trauma center in nearby Portland, where she undergoes surgery and is placed in the Intensive Care Unit. Her grandparents and other relatives arrive, as well as her best friend Kim. Eventually, Adam, her boyfriend, drops in to see her.

As the hours pass, Mia goes back and forth between observing what is happening around her and reflecting on her life up to this point. Her memories include being present at the birth of her brother, her father's transformation from a hard rocker to a teacher, her friendship with Kim, her love for music and the cello, her ambitions to become a great cellist, and falling in love with Adam. Mia hears a nurse say that the young girl's life is not in the hands of the doctors or the machines. It is Mia herself who is in control of whether she lives or dies. Mia begins to consider what her life would be like if she stays. Eventually, she determines that although having her die will hurt those who love her, they will recover. It is too difficult to think about living in a world where she has suffered so much loss. However, before she can let go, Adam arrives and puts headphones over her ears, allowing her to hear a piece of music by her favorite cellist, Yo Yo Ma, whose concert they attended on their first date. This causes Mia to think about not only what she has lost, but also about what might still be ahead of her. She summons all of her strength to squeeze Adam's hand, signalling her choice to live.