“The Duff” the book and The Duff the movie are too very different but very good stories. As much as I enjoy the film being a modern breed of teen comedy, the book is my favorite. Kody Keplinger crafts a story that at its core is about self-esteem, promoting body and sex positivity — almost a rarity in most young adult novels. The movie stays away from that, following the overly used Pygmalion formula. For what it’s worth, the film is incredibly charismatic, thanks to Mae Whitman and Robbie Amell. Too bad they couldn’t have channeled that into the same story set forth in the book.