not that the MC is a ghost or something but just that feeling a book gives off when you only know the characters' first names (how should a person be sheila heti) or you dont know their name at all (whereabouts jhumpa lahiri). even the autobiography of alice b toklas is sort of like this because toklas didn't actually write it and it's barely about her.
like they obviously exist in the world of the story but because you have less details and definitions, there's no question that you are reading a story as you read. when the characters are sort of enigmatic or allegorical it leaves more room for imagination and projection. makes them more of an idea than something you have to physically picture which is dope