First Person (Central Narrator)
Professor Grant Wiggins, the protagonist, is also the (kind of grouchy) narrator of the novel. That grouchiness puts a pessimistic filter on everything we get to see, so we have to take into account that Grant is probably leaving out most of the positive aspects of life on the plantation and really zooming in on the negative.
Grant tells us everything we need to know, almost always from his own point of view. However, when he wasn't there for something he figures out a way to pass the gossip along secondhand.
For example, in the very first paragraph he says,
I was not there, yet I was there. No, I did not go to the trial, I did not hear the verdict, because I knew all the time what it would be. Still, I was there. I was there as much as anyone else was there. (1.1)
This fast and loose treatment of narration is pretty cool, because we trust that Grant is telling us the truth, but we also let him get away with telling us interesting or vital information without having to have actually witnessed it. This narrative trick lets us in on some information about the kind of community we're dealing with: everyone knows everything about everybody else. It's a tight-knit group, and we're getting an insider's perspective on it.
It's also important to note that Chapter 29 is made up entirely of entries from Jefferson's diary, so it is actually from his perspective, not Grant's. But since Jefferson made sure Grant got his diary after he died, we can imagine that Grant is the one who made it available to us in his role as our fearless narrator.