The Rules of Survival by Nancy Werlin

Teenager Matthew, Callie who is twelve and much younger Emmie struggle to survive under the frightening, unpredictable care of their increasingly crazy mother. Mom demands absolute love and loyalty and the punishment can be terrifying if not brutal such as the time she drove on a free way against traffic until the kids pledged their love. She stalks former boy friends and other wise terrorizes many of the people who she knows but won't be manipulated by her.
So it is that three caring adults don't know how to help the kids without making things worse for every one. They are Matthew and Callie's father who could easily get custody of his kids but would have to leave Emmie behind. The kid's aunt, their mother's older sister who grew up being terrorized by her. Finally there is Murdoch the kids met after the witnessed him stopping a father from harming his son in a grocery store. Looking back two years after the events of this book took place, Matthew relates the years of abuse in a long letter to Emmie while he tries to come to terms with his horrifying knowledge that he was capable of ending his and his sisters' suffering in a very violent and final way.
jdw 10/16/06