Author Jeanne DuPrau primarily uses the third-person point of view throughout The City of Ember. However, her story also has two protagonists, Lina and Doon. A protagonist is a main character who changes and grows as a result of facing the conflict in the story and reaching the resolution. Therefore, DuPrau focuses on these two characters by using, more specifically, third-person limited point of view, shifting her focus in alternating chapters between Lina's perspective and Doon's perspective.
In third-person point of view, the narrator stands outside of the action in the story and relays the story as the action unfolds. Since the narrator is not any of the characters in the story, the narrator will address all characters by names and by using third-person pronouns such as he and she. We can easily recognize that the story is written in third person by looking at the prologue of the story. The prologue explains the builders' conversation about ensuring the citizens know how to find their way out of the city after 200 years. Since the chapter refers to the builders in third person, we know the story is narrated in third person, as we see in the opening sentence:
When the city of Ember was just built and not yet inhabited, the chief builder and the assistant builder, both of them weary, sat down to speak of the future. ("The Instructions")
There are several different types of third-person point of view, including third person omniscient, third person objective, and third person limited. The third-person limited narrator is able to know only the thoughts and feelings of one single character, usually the protagonist, and focuses on sharing these thoughts and feelings. The third-person omniscient narrator is able to see all and know all, for each character.
Later, in the opening chapter, the focus of the story shifts to Lina's thoughts and feelings; therefore, we know the author is now using third-person limited point of view. For example, in the opening chapter, the narrator informs the reader just how much Lina wishes to be assigned the job of messenger:
Lina was making her wish in pictures rather than in words. In her mind's eye, she saw herself running through the streets of the city in a red jacket. She made this picture as bright and real as she could. (Ch. 1)
As the story progresses, the narrator sporadically uses multiple chapters to shift to focusing the story on Doon's perspective rather than on Lina's. For example, chapter 3 is about Doon's first day on the job at the Pipeworks, whereas chapter 7 gives the reader a look at Doon being angered by the mayor's speech at the town meeting, and other chapters show Doon either in the Pipeworks or in the library.