I'll provide you with the three major themes of the novel.
"Alienation and Abandonment" is at the heart of Rusty-James' problems. His mother has deserted the family and he still suffers from having been left alone for three days by his father when still a child. His hero and brother, The Motorcycle Boy, comes and goes as he pleases, and Rusty-James worries that he will one day leave him for good. He is never happy when alone and he craves large crowds. Like many of the confused young boys in S. E. Hinton's novels, Rusty-James is an outsider, looking for his place in the world around him.
"Poverty". Rusty-James and his family are much worse off financially than most of the characters in Hinton's previous teen novels, The Outsiders and That was Then, This is Now. Rusty-James's father is an intelligent man and former attorney who has sunken to the depths of alcoholism. He has no job and the family exists on a meager welfare check which the father uses mostly for booze. The boys have little food to eat and rotate on the cot and mattress in the "crummy" apartment. Consequently, both of the brothers resort to petty crime to make ends meet.
"Death in Life". Nearly all of the characters are living hopelessly dead end lives, and the finale of the story offers little hope for them. The two brothers feel no real love, and The Motorcycle Boy is already color-blind and partly deaf. He will die tragically at the end of the story. Rusty-James is one of the least intelligent of all of Hinton's characters, and he admits to stumbling through life in a "fog." Even the river is stinking and "stagnant," one that will not even provide life for the Siamese fighting fish that The Motorcycle Boy dies trying to release.