Who are the ghosts of Hill House?

Up until I had actually read the last few pages of The Haunting of Hill House, I was convinced that there would be some sort of plot twist, that the entire story had actually been Eleanor as a ghost living out a fancy, and either imagining all of these characters, or imagining that they were actually interacting with her. In support of her being a ghost: in the beginning of the book she was convinced she had already been to the house. This could have been previous memories of living at the house tainting her current fantasy of being “Eleanor,” a living person visiting for the first time.

Secondly, the house is reaching out to her specifically. It is writing her name on the walls asking her to come home, speaking to her in the night, telling Mrs. Montague to ask her to return home. This could be other ghosts, or even the house, attempting to get back in touch with Eleanor, and bring her back to their reality.

Thirdly, as she spends more time in what might be considered a “fantasy” world, she gains a sort of response to the house, an ability to feel it and what happens inside it. She becomes the one who is banging on the doors, the cause of the bumps in the night. And then she is drawn to climb the staircase in the library, to reach the place where “she” had hung herself.