The Rules of Survival by Nancy Werlin

Living with an viscious, manipulative, and violent mother has taught Matthew how to survive and shelter his younger sisters from their mother's abuse. And then one day, a ray of hope:

"For me, it all started when I saw Murdoch stare down an angry father twice his size who was about to start pounding on his son. I heard him tell the little boy that no one had the right to hurt him, no one, not even his father. I'd never heard anyone say that before. I was thirteen years old, and what I thought I knew was that no one could be trusted. Especially the people who said they loved you.

"I was about to learn that I was right. And that I was wrong." 

This book is about a group of people, ordinary in their lives and demeaner, who, when confronted by evil have the courage to stare it down. As Murdock explains to Matthew, quoting the great bard himself, "Some are born great, some achieve geatness and some have greatness thrust upon them." Mathew and Murdock were not looking for greatness, nor were their family and friends, but each achieve it in their own way, in the the nick of time.