Ta da. I read it ages ago and felt quite interested in it.
This is an inner journey so you should focus on the development of maturity. I try my best to remember what I read.
There's a twist of lies and truth in here. There's one girl who dares write a letter to an unknown girl and then readily pours her heart out to this stranger basically because her expectation is too high. If you read Great Expectation of Charles Dicken, you can understand what people really mean when saying 'Great Expectation'. I'm going to the boring part: analysis. I hate those sorts of clearcutting the text like this but anyway, hope my teacher's method gives you some ideas
Catalyst: the enthusiasm, anticipation of a naive teenager desiring to explore the life through a few pages of letters.
Journeys: perserverance despite being deceived, sympathy to empathy: a jump in humanity.
Destination: reconciliation (first stage), self-actualization (second stage), life-recognition and a yearn to desperate change.
I think from here you can get some quotes from there. Quite simple. The plots that put a climax, I suppose, aree when the lie is revealed and one girl attempts to re-contact and when the prisoner tells about her life and all those changes occuring inside the detention centre.
You can mention the effective style of experiencing a story through the views of characters: very entertaining, mesmerizing, strange as well.
Cheers.