Chocolat by Joanne Harris

I'm writing a critical essay on Chocolat by Joanne Harris. I've been asked to choose a novel in which a character appears to change, outline the nature of the change and discuss how this illuminates the themes of the text.

I've chosen to do this through word choice and narrative technique, and the latter is what I'm having trouble with.

Should I write about how the book is set out in a kind of diary form?

What kind of things are appropriate to narrative technique?

Anyone who has read the book or has any ideas that could help, it would be much appreciated