There is really good essay by Rob Roberge at The Rumpus about the particular kind of first person point-of-view that F. Scott Fitzgerald used in The Great Gatsby. Roberge calls it “Flexible First Person.”
It’s really just a technique a writer can use within the confines of traditional first-person. It’s not a POV of its own, but more of a subset technique within a POV choice. It’s the technique of a writer who realizes there are a multitude of ways that we (who live in First-Person Singular—most of us, at any rate) get information about other people and events.
Think about it—there are plenty of things we know about in life that we weren’t present for. People tell us things, we listen to the radio, we read, we watch TV and check the Internet (though the last two weren’t available to Fitzgerald) and, perhaps most importantly, we imagine what other people are thinking.
Still one of my favorite novels. Makes me want to read it again. There are so many wonderful things about that novel, most especially the crystalline grace of Fitzgerald’s prose.