I love that book, and I remember how it said that John Thornton was Buck's last tie to civilization, And once he died Buck was free to go primitive without anything holding him back. Loving him caused Buck to be unsure of himself and his primitive identity.
The point of view that this story is written in appears to be Third Person Limited Omniscient. This is due to the narrator having knowledge of only the boy's thoughts and feelings; but at the same time, the boy in the story is not the one narrating.
Another way to tell that it is Third Person, is due to the narrator using pronouns like, "He" and "His".
