I've just started reading Lonesome Dove and am already suspecting Larry McMurtry might be ILI. I think he writes Ni and Fi really well in characters and also that his book seems to written in something I feel is an Ni style so far. That said, I'm not really getting married to this idea. I can change my mind. (It's not that all of his characters are Ni and/or Fi or anything like that imo; but that I just recognize it when it shows up and I just get this feeling it may show up so well because it's central to the author himself.)

PS: these are tentative thoughts only (as in speculations arising of this moment given where I am in reading the book) not a sort of final word of "one of the characters looked dreamy-eyed so the author just must be Ni" or such nonsense.