Who is Marcus Brewer from About a Boy and what is their importance?

Marcus Brewer is a twelve-year-old boy when this novel begins. The reader quickly learns that Marcus is the son of a single mother who is deeply depressed. Marcus struggles with his mother's illness alongside her, afraid from one moment to the next that his mother might attempt suicide and leave him alone. In fact, Marcus spends a portion of the novel attempting to find a man for his mother so that he will not be alone if she should die. This leads in part to the strong relationship that develops between Marcus and Will Freeman.