The Blue Castle

L. M. Montgomery is perhaps best known as an author of youth fiction, especially her Anne of Green Gables series. But of her novels intended for adult readers, The Blue Castle is the most famous.
In Valancy Stirling's rural Ontario town, marriage is thought to be a young woman's vital accomplishment. Yet Valancy, now in her late 20s, has never had a flicker of interest from any suitor. Add to this the oppressive home life she endures with her mother, and Valancy's misery is complete. In order to find some relief, she builds a fantasy world in her imagination—her "Blue Castle"—full of love and beauty. Even this, however, fails to support her when her chest pains prove to be the sign of a terminal condition.
This traumatic discovery combines with Valancy's inspirational reading to prompt her to take back her life—much to her relatives' consternation. Undeterred, Valancy finds new worth and freedom in relationships she could never have imagined before, which bring their own surprising twists and turns.