In Chapter 4, the narration focuses on the teenage Gogol, from the family party to the scene in which he receives his father's precious book, to the long trip overseas, and on into Gogol's high school courses and to a college party he attends. Chapter 5 begins with an unusual paragraph in which the narrator gives us a detached commentary on famous people who have changed their names; it is here that you might say that the narration is truly different than anywhere else in Chapters 4 or 5, where it's focused on something more than a faithful report of what the characters are doing. The chapter then focuses again on Gogol as he completes the process of changing his first name. We stay with him as he attends college at Yale, developing a sense of independence and trying to become the different person that he feels should be "Nikhil" instead of "Gogol." The narrator describes Gogol's brief but intense relationship with Ruth, then ends the chapter with Gogol's heart-to-heart conversation with his father as he learns about the train accident in the past. Even though Ashoke is a key figure in this scene, the narration keeps a spotlight on Gogol, highlighting his feelings and reactions to the revelation.
Throughout the novel, the narrator is a particularly interesting voice; she follows individual characters for a while, then flits to others as the story heads in a different direction. Chapter 1 follows Ashima, then Ashoke; Chapter 2 follows them both but focuses more on Ashima and her growing relationship with the infant Gogol; Chapter 3 focuses on the little family as a unit, then veers off to follow Gogol on his school field trip. Like I described above, Chapters 4 and 5 are really all about Gogol, but further chapters veer off to follow other characters. The narrator even spends time on Moushumi alone when she's having her affair, toward the end of the novel, and later on Ashima again, middle aged and alone.
Throughout these transitions, the narrator's voice is smooth and factual, describing objects and characters and movements with minute precision, offering subtle cultural insights along the way. And while it's startling at times for readers to be given information by the narrator that none of the characters has access to--like whether or not something will ever happen again in a character's future--perhaps an even more fascinating thing that the narrator does is continue to call Gogol by his pet name ("Gogol") long after he changes it to his good name, Nikhil. It's as if the narrator has sided with Gogol's sister Sonia, insisting that government paperwork means nothing and that Gogol cannot ever change his name because it's who he is.
I mention all of this because we should consider the narrator's tendency to switch the focus from one character to another as one interesting and enduring aspect of The Namesake's narration, rather than a fluke or an error in the storytelling.