What is the author's style in the novel, The Night Diary?

The Night Diary is not divided into chapters or sections as most fictional novels written for young adults, but rather, is an epistolary novel, told entirely through the medium of letters written by Nisha to her late mother. The book is thus divided into a long series of letters, some short, some long, which detail the events of a day in the life of Nisha and her brother Amil. Each letter begins with the words, “Dear Mama,” and ends with the words, “Love, Nisha.”