Undressing the moon / T. Greenwood.

Enhanced descriptions from Syndetics:

As a child, Piper Kincaid always felt her mother was on the edge of leaving. And then the summer Piper turns fourteen, it really happens. Devastated by this loss, and the rejection she feels from her increasingly distant father, she finds an uneasy comfort with an older man who is equally riddled with sorrow. Discovering desire for the first time, Piper is at first fascinated and strengthened by the attention. But with time, the growing weight of their secret and his need begin a devastating avalanche of events neither is able to control nor understand. Now, Piper is thirty years old and dying of breast cancer. Reflecting on her life, she is drawn ineluctably back to that summer and haunted with regret. As she attempts to reassemble the fragments of her history, what emerges is the kaleidoscopic portrait of a young woman whose indefatigable spirit prevails, despite shattered dreams. An evocative, richly-told novel of coming-of-age and coming-to-terms, Undressing the Moon finds grace in wreckage and hope in a broken life.