The love of literature
The love of literature is perhaps the most important theme in Checkout 19. The narrator/young woman in Checkout 19 has a deep and abiding love for—though some may call it an obsession with—literature. The narrator not only loves literature, but she also recognizes just how transformative it can be. Because of her love of literature, she can leave her uninteresting world and escape into a fantastical world. Worlds in which she can learn quite a bit and worlds in which she can be entertained. Though the narrator's love of literature brings her good things and gives her an outlet, it brings her negative things too—like depression, suicidality, and other mental health issues.
Fantasy as a coping mechanism
To escape her relatively benign and uninteresting life, the unnamed narrator/young woman escapes into a world of fantasy by reading her books. Using fantasy as a coping mechanism is an important theme in Checkout 19. The main character in the novel dives into her fantasy world, which is warm and comfortable for her, to escape her more difficult life in the real world. Not only does this characterization make the narrator a more well-rounded and deep character, but it also underscores the importance of having a healthy outlet to keep sane in readers' minds.
Feminism and female empowerment
Feminism and female empowerment is one of the most important themes in Checkout 19. The main character and protagonist of the novel—the unnamed narrator/young woman—is an avowed feminist. She also is deeply committed to female empowerment and often takes her destiny into her own hands. In other words, she is unlike many people in the world and lives her life in accordance with her belief systems.