Undressing the Moon — T. Greenwood

In evocative shards of memory, a terminally ill young woman pieces together her family's difficult past in this “lyrical, delicately affecting tale” (Publisher Weekly).
 
At thirty, Piper Kincaid feels too young to be dying, even as breast cancer eats away her strength. Yet with all the questions of her future before her, she's adrift in the past, remembering the fateful summer she turned fourteen and her life changed forever.

It was back then that what Piper dreaded came to pass: her restless, artistic mother, finally left. She had a brother who loved her, but her mother's absence, her father's distance, and a volatile secret threatened to shatter her whole world. Now Piper is back in her hometown of Quimby, Vermont -- and once again left with the jagged pieces of a broken life. If she is ever going to survive, she'll have to begin with the summer that broke them all.