Jean Perdu is a 50-year-old bookseller who runs the Literary Apothecary, a floating bookstore moored on a barge on the Seine. He views himself as a literary pharmacist, prescribing books to treat emotional ailments that doctors cannot diagnose. Highly perceptive of others' feelings, he lives a detached, highly regimented life to cope with the lingering grief of his former lover's departure 21 years ago.

Max is an author in his twenties who lives in the same building as Jean Perdu. Having achieved sudden fame for his debut novel, he now suffers from intense writer's block and hides from fans and the press by wearing large earmuffs and sunglasses. He seeks Jean's mentorship as he tries to rediscover his creative voice and escape the pressures of his success.

Catherine is a sculptor moving into Jean Perdu's building following a painful divorce. Left with almost no furniture, she receives a table and chair from Jean, setting off a comfortable and understanding friendship. Empathetic and nurturing, she focuses on returning to her creative passions while managing the pain of her recent separation.

Manon is a vibrant, passionate woman from the Provence region of southern France who had an intense, five-year affair with Jean Perdu. Described in Jean's memories as fiercely connected to her body and her senses, she possessed a joyous appetite for life. She left Jean over two decades ago, resulting in his profound isolation.

Salvatore is an Italian expatriate living in France who has spent years wandering the river networks and taking odd jobs. A talented cook and a hopeless romantic, he claims to be searching for a woman with whom he spent a single night long ago. He joins Jean and Max aboard the Literary Apothecary, using his culinary skills to awaken his friends' appreciation for good food and community.

Luc is a winemaker from the Provence region and Manon's fiancé. Described in Manon's diary as understanding of her need for freedom, he represents the grounded, agrarian life of her hometown. He tends to the vineyards while accepting Manon's complex heart.

Samantha is the energetic head of the Cuisery business guild. After being pulled from the river by Salvatore during a fierce storm, she joins the men aboard the Literary Apothecary. She is deeply involved in the local book trade and travels with three packed suitcases, ready for adventure.

Madame Bernard is the owner of the apartment building at 27 Rue Montagnard in Paris. She looks out for her tenants and pushes Jean to be neighborly to the new resident.

The concierge at 27 Rue Montagnard. She assists in the daily operations of the building and joins the landlady in convincing Jean to help Catherine.

Joaquin is Jean Perdu's father. He maintains a weekly habit of visiting with his son to discuss life and women, while often using Jean as a messenger to communicate with his estranged wife.

Anna is a customer at Jean's floating bookstore. After Jean initially refuses to sell her the book she requests, she returns, tearful but receptive, allowing him to prescribe the literature that actually fits her emotional state.

Victoria is a quick-tongued young woman from the Provence region. She works the land and immediately catches Max's attention when he and Jean get lost driving near their rented vacation home.

P.D. Olson is a famous American writer living in France. He takes Jean and Max to a secret tango club in an old schoolhouse and encourages Jean to loosen up and dance.

Javier is a friend of Salvatore Cuneo who lives in an artistic country town with his family. He offers the travelers a place to rest and share a meal, though he harbors strong opinions about Salvatore's nomadic lifestyle.

Zelda is Javier's wife. She lives in a large house in the French countryside, helping to host Salvatore and his companions during their river journey.

Elaia is Javier and Zelda's twenty-something daughter. She has battled cancer since she was a young girl and maintains a free-spirited, artistic approach to life, quickly forming a connection with Max.

Leon is the son of Javier and Zelda, living with his family in an artistic, rural town along the river network.

Brigitte Bonnet is a local in the South of France who rents a room to Jean and Max. She provides them with regional hospitality and gives them a safe place to stay while they explore the countryside.

Kafka is one of the two stray cats that frequent the Literary Apothecary. He acts as a quiet companion to Jean on the barge.

Lindgren is a stray cat that visits Jean's floating bookstore, enjoying the safety and food provided on the river barge.