A.J. Fikry is the 39-year-old hardened owner of Island Books on Alice Island. Following the death of his wife, Nic, he has become a bitter, isolated widower who self-medicates with alcohol. He strictly adheres to rigid literary tastes and aggressively pushes people away. His monotonous routine faces a drastic upheaval when a rare book is stolen from his apartment and a toddler is abandoned in his shop.

Amelia is a 31-year-old sales representative for Knightley Press. Replacing the late Harvey Rhodes, she is an ambitious but sometimes clumsy professional who specializes in small, independent bookstores. Despite her disastrous first meeting with A.J., she maintains her professional dignity and deeply values the emotional resonance of fiction.

Maya is a bright, trusting two-year-old girl who is suddenly abandoned in A.J.'s bookstore. Described as cerebral and highly observant, she quickly takes to A.J. and becomes fascinated by the literary environment surrounding her. Her arrival fundamentally shifts the emotional landscape of the island.

Ismay is Nic's sister and A.J.'s sister-in-law. She works as a drama teacher and is pregnant after suffering multiple previous miscarriages. Ismay struggles to maintain a facade of happiness in her strained marriage to a successful local author, masking her insecurities with an appreciation for fine things.

Daniel is Ismay's husband and a successful author living in the area. Handsome and deeply self-absorbed, he prioritizes his writing career and personal pleasures over his marital commitments. He frequently acts unfaithfully and seems more interested in literary parties than supporting his wife through her medical struggles.

Chief Lambiase is a hardworking police officer on Alice Island. Initially brought into A.J.'s life to investigate a burglary, he proves to be a loyal presence in the community. He embraces a newfound interest in reading, eventually starting a police book club at Island Books.

Nic is A.J.'s deceased wife who died in a car accident while two months pregnant. She originally met A.J. in a PhD program before they abandoned academia to open a bookstore in her hometown. Even after her death, she heavily influences A.J.'s thoughts and appears to him in his sleep.

Marian is a smart 22-year-old woman who travels to Alice Island under desperate circumstances. Facing insurmountable struggles, she makes the heartbreaking decision to leave her toddler in the care of a bookstore owner, leaving a note requesting that he teach the child to read.

Harvey was the previous publisher's agent for Knightley Press and one of the few people whose literary recommendations A.J. truly respected. His sudden death removes one of A.J.'s last remaining connections to the publishing world and exacerbates the bookstore owner's profound sense of isolation.

Molly is the assistant at Island Books. She helps keep the store running while A.J. retreats into his grief and drinking, though A.J. frequently finds himself frustrated by her presence and lack of enthusiasm.