Yikes! Good question!
The character of Frank McCourt, in the autobiographical novel Angela's Ashes, changes significantly as the story progresses.
We first see Frank in a dependent role as the U.S born son of Irish immigrants who came to New York as a basic experiment. He is taken back to Ireland and goes back of welfare, poverty, rejection, and the psychological abuse that he endures during his childhood years, both at home and in school.
His adolescence is no picnic either. He witnesses the abandonment of his father, the "selling off" of his mother to a far cousin for the sake of having a place to stay, living as a peasant in his household, and beginning to feel the force of rebellion building upon his mind- which is a very prosperous one, to say the least.
We witness his first love- a girl with a terminal case of tuberculosis- and his self discovery: He has to return to America. Once there he discovers his second big thing: He has acquired his father's own drinking disease. Just before he sees himself becoming Frank Senior, he tries to change.
In America, where he works as a cook in New York city, he mingles with Puerto Ricans, African Americans, and faces the reality of working in places which post outside their doors signs such as "No dogs, no Irish, no Puerto Ricans, no blacks" while these were the very people (except for the dogs :) ) working in the back of the kitchens.
Overall, the story aims to show how, at all times, Frank kept the teachings of his mother close to his heart: Do not allow anyone to humiliate him-stay alert-and, above all, survive.
Up until the end of the novel we can appreciate that Frank McCourt has a consistent flow in his narrative: Thankfulness. This is why, in the end, when they asked him whether America was a great country, he answered in his natural brogue the phrase which would become the title of his next novel" " 'Tis ".