I assume that the "main points" refer to the themes of the book. If you go to the links below, you will get complete details of the themes and characters. I will summarize them briefly for you.
This is the story of Bryon Douglas and his journey to manhood when he realizes he must find some sense of his moral responsibility to himself and other people. It is a difficult journey within the environment of gangs, violence, and the use of alcohol and drugs. Bryon realizes he must clean up his act, requiring him to turn Mark into the police in the end.
Mark is like a brother to Bryon, but Bryon can no longer condone the gang life he participated in as a boy. Mark wants to recapture the closeness he and Bryon shared during those years, but Bryon has recognized what gang life has done to himself and to Mark. Bryon tries to get Mark to realize the benefit "when you know your own personality so you don't need the one the gang makes for you." Mark has no conscience, however, and wants to go back to the time "when we were like brothers, not just you and me, but all of us together. We woulda died for each other then."