What is the author's style in Picture Perfect by Jodi Picoult?

Jodi Picoult's narrator changes throughout this story. Much of her narration is omnipotent, as she describes the scenes and the characters through dialogue and description. However, Picoult also has Cassie Barrett Rivers, her protagonist, become the narrator, as one realizes that Cassie is telling her story to Will Flying Horse when she escapes from Alex's abuse to South Dakota. However, the story is written primarily from the omnipotent view of the author, and the deviations into other narrators are only for effect. For instance, there are several entries preceding the chapters that are simply old Indian legends, told from an omnipotent viewpoint. It is clear that these are not Picoult's or Cassie Barrett's stories, but just come out of nowhere and relay a poignant message that is relative to that part of the story.