That was Then, This is Now is a young adult novel written by SE Hinton.
Bryon and Mark have been friends forever, and are closer than brothers. When Mark is left 'parentless' he goes to live with Bryon and his mother. They are poor kids, living in a city ghetto, during the beginning of Hippies and the Vietnam Draft, and the end of the Greasers.
These boys date girls, smoke lots of fags, cruise, skip school, get in fights, and hustle pool games. Then things start to change. Bryon meets Cathy. He's always been a good student in school and he stays focused academically and even gets a job. Mark, on the other hand, doesn't change and can't understand Bryon. Mark just lives in the moment, for the action.
Then something happens- Bryon makes a discovery about Mark and his choices will affect both boys for the rest of their lives.
I've read 2 other books by Hinton, RumbleFish and The Outsiders. All three novels have the same theme, same characters, same story line concepts. But she does appeal to the young adult reader, and this novel specifically, is at the 7th grade reading level and are classroom teachable, which was my whole purpose for reading it.
Hinton fans will continue to be fans.