Shelly provides multiple perspectives (narrative shift) throughout three volumes of the same story. In each of these volumes, you learn the perspective of Walton, Frankenstein, and Adam (AKA the creature). This allows the reader to develop for themselves who they believe is guilty and come up with their own interpretation of the story. This allows for a more reliable narration because if only one perspective is given, how would you know they weren't just lying or giving a bias interpretation?