One True Thing by Anna Quindlen
A young woman is in jail accused of the mercy killing of her mother. She says she didn't do it. Ellen Gulden is a young, successful New York journalist. When her mother gets cancer, her father, a university professor, insists she come home. As she looks after her mother, their relationship - tender, awkward and revealing - deepens and Ellen is forced to confront painful truths about her adored father. But as Kate lies dying, and in the weeks that follow her death, events take a shocking and unexpected turn. Family emotions are laid bare as a new drama is played out: between Ellen and her brothers, between Ellen and her father, and in court.