In this book Twenge is really good at giving the audience background knowledge about herself and about the research that she did for the book. If you are familiar with the audience that you are writing to it is easier to persuade them, because you know there interests.
I think that Twenge did a good job assessing her audience by asking herself questions like, who is going to read what I am going to discuss, what are their backgrounds, how much do the readers know about the topic I am writing about, and how much background information should I provide to my audience. I feel that when I read this book I can relate and easily understand what she is discussing. She is writing to a younger audience and not to Biochemists.
I like the form of genre that Twenge uses in Generation Me. She breaks each chapter in to sub categories to put emphasis on specific topics which allow the reader to see what she thinks is important information. In this book she uses simple language with strong interests to get her point across. Structure is very important to the reader and the writer. Different types of magazines and novels have specific formats and structures of how they should be written. The style of writing is starting to change slowly over time just like fashion changes, but it will always be important to consider your audience when formatting the genre of your book.