What are the major events or memorable events that happened in the book That Was Then, This Is Now?
In S. E. Hinton's novel, many memorable events take place; this answer will focus on the events that impact Bryon's changing attitudes towards his life and his previous self.
When Bryon meets Cathy, his emotional life begins to change in a significant way, making the start of their dating relationship a memorable event in the novel. Cathy's maturity, integrity, and kindness all have a positive influence on Bryon in a general way, but her influence also leads Bryon to separate himself from Mark.
While dating Cathy, Bryon matures and develops a conscience, which renders him unable to stand by and watch Mark knowingly damage lives with his drug dealing. This event is critical to both the plot and to the character development of both Mark and Bryon, and it leads to another significant event that displays Bryon's complete disengagement from Mark.
When Bryon betrays Mark, a third memorable incident in the novel, Bryon's adult self—who is honest, responsible, and caring—emerges. Though Mark is like a brother to Bryon, Mark's actions have become unacceptable; by rejecting Mark, Bryon is rejecting his previous self, choosing instead to be a good person.