What is the author's style in Sophie's World by Jostein Gaarder?

The point of view of the book is third person. There is a narrator who knows the thoughts of Sophie. In the beginning of the book, until the chapter "Bjerkely," we are told the story through Sophie's eyes and her inner thoughts. After Hilde is introduced in the chapter "Bjerkely," the story alternates point of view between Hilde and Sophie, as Hilde reads the book about Sophie and philosophy. As the Major finally comes home from Lebanon, the point of view in that section is from the Major's point of view.

The last chapters are complicated with the point of view shifting rapidly from Sophie and Alberto after their escape, when they have joined the invisible people, and Hilde and her father. Finally, the last chapter, "The Big Bang," is written in mimicry of a Platonic dialogue, which is between Hilde and her father, Major Knag, with Sophie and Alberto as unseen observers, who say and do things unseen by the others.

The point of view of the book is complicated in that it presents a book within a book. Long passages are philosophy lectures by Alberto. They seem to be taken in large sections from an actual history of philosophy textbook. However, they are also part of the story of Sophie's education in philosophy, and her reaction to the strange events around her. The shift in point of view is in the chapter "Berkeley" to the chapter "Bjerkely." First the stage is set for the transition, and then there is a transition to the point of view of Hilde. It is made known to the reader that Hilde is reading a book about Sophie and Alberto's adventure in philosophy. In turn, the story of Hilde is part of a book about her relationship with her father, and her father's desire to educate her.