During the Second World War, London-based author Juliet Ashton begins receiving letters from residents of Guernsey, who tell her about a book club formed during the German occupation. Intrigued, Juliet decides to travel to the island to meet them in person and uncover the story behind the club's unusual name. There, she encounters a group of very different people, all marked by the hardships of war, but united by books and friendship. Little by little, Juliet becomes entangled in their lives and secrets, particularly the story of a former club member, which will change her outlook on life, love, and writing.