The unnamed narrator is a 26-year-old, Ivy-League-educated woman living in a luxury Upper East Side apartment. Blessed with physical beauty and a substantial inheritance from her deceased parents, she nonetheless struggles with deep apathy. She hatches a deliberate plan to use prescription medication to sleep away a year of her life, seeking an escape from the daily burden of human consciousness.

Reva is the narrator's best friend from college and works as an executive assistant at a Manhattan insurance brokerage firm. Coming from a middle-class background, she strives to fit into the wealthy, elite lifestyle her friend inhabits effortlessly. She struggles with bulimia and deep-seated insecurities, often relying on alcohol and self-help literature to cope with her unhappiness.

Dr. Tuttle is an eccentric, scatterbrained psychiatrist practicing in New York City. She readily prescribes a staggering array of heavy sedatives based entirely on the narrator's fabricated claims of insomnia. Unprofessional and given to spouting pseudoscience, she inadvertently enables the narrator's extreme isolation project.

Trevor is a banker who met the narrator when she was an 18-year-old college freshman. Fifteen years her senior, he treats their relationship with a cold, businesslike efficiency. He typically only reaches out to the narrator when he feels rejected by women his own age, using her for validation.

The narrator's mother was a distant, unapproachable woman who struggled with an alcohol addiction during the narrator's childhood. She spent most of her time sleeping or drinking in her bedroom, providing her daughter with very little affection or warmth. Her tragic death leaves a lasting emotional void in the narrator's life.

The narrator's father was a science professor at a university in New York. He maintained a strained, loveless marriage with his wife and acted like a stranger to his daughter. His battle with cancer and subsequent death during the narrator's college years initiates her profound isolation from the world.

Ping Xi is a young, pretentious artist from Southern California who creates shock-value pieces for the gallery. He becomes an unwitting participant in the narrator's drug-induced blackouts, eventually agreeing to facilitate her hibernation in exchange for permission to document her for an art project.

Ken is an executive at the Manhattan insurance brokerage firm where Reva works. He uses his position of power to carry on an illicit affair with his assistant, enjoying the benefits of the relationship without offering Reva any real commitment or respect.