Reflective, Nostalgic, Sentimental
Have you ever retold a story from your childhood? There were certain things you emphasized (hey, childhood is vivid) and others you left out or just plain forgot, right? Well, Annie John is about remembering the past. All the verbs are in the past tense as every event, situation or circumstance described in the book is a memory. We can assume that our narrator, Annie, is remembering these moments of childhood as an adult.
I don't know why seeing that [barge] struck me so, but suddenly a wave of strong feeling came over me, and my heart swelled with a great gladness as the words "I shall never see this again" spilled out inside me. But then, just as quickly, my heart shriveled up and the words "I shall never see this again" stabbed at me. I don't know what stopped me from falling in a heap at my parents' feet. (8.17)
Not only is the tone reflective, but also it is often nostalgic and sentimental, especially when she recalls early moments of blissful existence with her mother:
How important I felt to be with my mother. (2.4)
She writes with the sentiment of childhood, while using aspects of the knowing nostalgia of adulthood: Kinkaid may know better now, but she still remembers how strong her feelings of love (and later hatred) were in those awkward years between childhood and adulthood.