This power point is a great way to teach author's purpose. It gives examples that pop up one by one explaining why an author might write. Students will enjoy the moving graphics and gain perspective on how to understand their reading based on their new knowledge of why an author chose to write a piece.
An active engagement activity I do with students is bring in various types of literature. I label 3 baskets: persuade, inform and entertain. As I show students each piece of literature (i.e. recipes, comic books, instruction manuals, etc.) they decide which basket it belongs in.