I used to think that things were quite simple in a story: you sympathise with one character, despise (or at least slightly dislike) another and root for the one you feel sympathy for. Although ‘good’ and ‘bad’ characters may not always be entirely discernible all the time, and even though characters may well be a mix of both, there is generally a character the reader favours more than another (I am guessing that most people would feel more sympathy for, say, Harry Potter than Voldemort).
But in some cases, this simple principle seems more difficult to apply.
In English class, I recently read Death of a Salesman by Arthur Miller. Throughout the play, I felt sympathy for the protagonist, Willy Loman, whereas some people in my class commented that he seemed annoying. I felt bad about his need to control the direction his life is moving in and his failure to do so, about his shattered hopes and dreams. Moreover, I disliked his older son, Biff, for being so hostile towards his father.
However, a twist in the plot revealed near the end of the story turned my whole viewpoint topsy-turvy.