These two verses have created an issue for understanding how Nephi wrote. Verse 17 declares that Nephi is abridging his father’s record, and that makes it seem as though he is changing his source. He abridged his father’s record, and now makes an account of his proceedings in his day.
The problem is that in the very next verse, Nephi will again pick up with his father’s story. Clearly, Nephi does not separate his and his father’s accounts at this point, nor anywhere in all of First Nephi. There will be a gradual shift in emphasis from his father’s story to his own, but not one marked by a specific change.
What we are seeing is an aside that Nephi inserted into his planned narrative. He had been speaking of his father’s visions and prophetic calling. As he wrote, that triggered a reference to his writing task. In these verses, he is speaking of his process of writing, not the historical narrative. Nephi is telling his own story, a story that he is in the process of writing on plates he made with his own hands. Yet, he knows he cannot tell his story without speaking of his father. He therefore notes that he will give a short account of his father’s call, and then will tell his story.
We can recognize these verses as an interruption because they follow a pattern that has been called repetitive resumption. In other literature, it might mark an inserted text or story, but in the Book of Mormon it typically represents an author’s insertion into his planned narrative.
The technique gets its name from the way the author returns to the planned narrative. Some essential part of the text from the departure is repeated, notifying the reader that the narrative had returned to the planned text. See 1 Nephi 6: 1-6 Part 1 for an explanation and examples of repetitive resumption.