Regret
Regret appears as one of The Midnight Library's main themes. In the present timeline of her life, Nora is filled with regret about her various choices. She often wonders how her life might have turned out differently had she made various other choices or taken certain risks. When she arrives at the Midnight Library, Nora is shown a book called the "Book of Regrets" which compiles the things in her life that she wishes she had handled differently. However, the book complicates this idea by showing Nora taking different paths but still remaining unhappy. In a life where she is stuck with competitive swimming, she is close with her brother and her father is still alive, but her mother is dead and she struggles with her mental health. In a life where she married her ex-fiancé, they own a pub together and are deeply unhappy. What she learns over the course of the book is that choices have consequences that can't be precisely predicted and that some regrets are more complex than they initially appear.
Purpose
Purpose is another major theme throughout the novel. Nora struggles to find meaning in her life. At the beginning of the novel, she loses her job at the music store as well as one of her piano students. Her cat dies and she is told her neighbor no longer needs her to deliver her medication. Feeling estranged from other people and lacking any real purpose in her life, she decides she no longer wants to live. What she discovers in visiting parallel versions of her life is that people do rely on her in ways she did not immediately perceive, and that her small actions (being a piano teacher, keeping her cat outside) actually have a definite positive impact on the world. In this way, by the end of the book, she develops a renewed sense of purpose and decides to keep living.
Loneliness
Loneliness is also a key theme in the novel. When she decides to end her life, Nora is driven by the feeling that she has no remaining connection to the people around her. She and her brother are on bad terms. She no longer speaks with her ex-boyfriend, Dan. She was acrimoniously fired from two jobs and she lives far away from her best friend, Izzy. She has the distinct sense that no one in the world loves or cares about her anymore and feels a crushing sense of loneliness. In this way, the book emphasizes the importance of human connection, as Nora being able to reach out to the people she loves at the end of the story helps her to regain her sense of meaning and happiness.
Possibility
Possibility is a major theme in the novel. The story begins with Nora playing chess with her elementary school librarian Mrs. Elm. She explains to Nora that many possible lives branch out from the minor decisions that people make every day, in the same way that a chess game can hinge on the placement of a seemingly inconsequential piece. This idea is expanded on when Nora enters the Midnight Library and is able to explore the repercussions of her actions. She discovers how wildly different her life could be as a result of seemingly small choices, like going on a date or teaching a piano student. At the end of the book, Nora realizes that her life is full of possibility, as she recognizes how much she can change things.
Success
Success is another main theme in the novel. In various versions of her life, Nora attains a certain level of success and renown in different careers. In one, she is a famous rock star with millions of fans. In another, she is a swimmer who has competed in the Olympics. In that life she delivers a speech reflecting on the nature of her success, noting how its definition is vague and how every life has its good and bad aspects.
Control
While the narrative contends with the impact of various decisions, it also notes how little control people have over these outcomes. In one life she decides to marry her ex, thinking that she was too hasty in breaking off their engagement. However, she finds that they are both unhappy in their marriage and that he cheats on her. In another, she sticks with her rock band and becomes famous, but learns that in that life her brother is dead and that she has had a number of difficulties with mental illness. In revealing the complexity of these lives, the book shows that Nora’s perception of these decisions as mistakes isn’t entirely accurate.
Love
Love is another important theme in the book. In different lives, Nora has different romantic partners. In one, she marries Dan and they own a pub together. In another, she is married to Ash and they live in Cambridge with their daughter. In another, she had a relationship with a famous movie star who she realizes is very shallow. In all of these lives, she finds various degrees of satisfaction and frustration. With Dan, she realizes she is deeply unhappy. With Ash, she feels content but somewhat unsettled. Through these different relationships, the book examines what Nora actually needs in a relationship, often showing how it contrasts with what might seem initially alluring, like dating a movie star.
