Odile is an independent, intellectually curious young woman living in Paris on the brink of war, and decades later, a solitary widow in 1980s Montana. She values financial independence and finds her true calling among the books and patrons of the American Library. She is fiercely protective of her loved ones but struggles with a fear of romantic commitment after witnessing family scandals.

Lily is a bright, inquisitive middle school student growing up in Froid, Montana, during the Cold War. She excels academically but faces bullying from peers and deals with shifting family dynamics. Her eagerness to learn about French culture sparks a transformative bond with her older neighbor.

Margaret is a wealthy English woman who feels isolated and out of place in Parisian society. Trapped in an unhappy marriage with her diplomat husband, she finds comfort and a sense of community at the American Library. She is generous but sometimes culturally insensitive to her French peers.

Paul is a young French police officer who courts Odile. He stands out to her by supporting her desire to work at the library, contrasting sharply with her conservative father's views. He is devoted to his mother and shows a protective streak toward the women he cares about.

Rémy is Odile's twin brother, a progressive law student who recognizes the looming threat of war earlier than most Parisians. He shares a close bond with his sister but frequently clashes with their conservative father regarding his future and political stances.

Bitsi is the small-statured but spirited children's librarian at the American Library. She quickly befriends Odile over their mutual love of books. Her developing romance with Odile's brother causes temporary tension within her social circle.

Odile's father is a conservative French police captain who firmly believes women should marry rather than pursue careers. Despite his traditional views and strict household rules, he demonstrates affection for his children through small, protective gestures.

A traditional Parisian woman who strictly adheres to societal expectations. Her harsh rejection of her divorced sister profoundly impacted her daughter's view of unconditional love. She prioritizes family reputation and stability over individual fulfillment.

The capable and dedicated American directress of the library in Paris. She models professional excellence and steady leadership, prioritizing the institution's mission and the well-being of her staff despite the looming international crisis.

A respected female professor at the Sorbonne and a devoted patron of the American Library. She serves as a role model of female academic success for Odile. She values the intellectual community the library provides.

Lily's best friend in Montana. She provides Lily with companionship and an escape from household tensions. Their teenage friendship involves shared secrets, typical adolescent jealousies, and fierce loyalty.

A hardworking bank employee in Montana who struggles to communicate emotionally with his daughter. He copes with family illness and grief by working long hours and watching television, leaving him somewhat disconnected from Lily's daily needs.

A woman who enters the Jacobsen family's life during a period of transition. She tries to build a relationship with Lily and manage the household duties, occasionally clashing with her new stepdaughter over chores and personal boundaries.

The head librarian at the American Library in Paris, formerly a Russian aristocrat who survived the Russian Revolution. He uses his past wartime experiences to offer perspective to younger staff members and acts as a steadying presence in the building.

Lily's mother, a warm woman dealing with chronic health issues. She tries to maintain normalcy in her household despite her declining physical condition, insisting that her family continue their daily routines.