I'm not sure exactly as I haven't read it in detail. But generally, it might be about a group of people who are the keepers of a house. Maybe they have some special duties or secrets related to the house.
Without having read the book, it's difficult to name the exact main characters. But it stands to reason that the keepers themselves are central. They could be individuals with unique personalities. For instance, one keeper might be very strict about the rules of the house, while another could be more lenient. There could also be a character who is trying to uncover the true nature of the house against the wishes of the keepers, which would make them an important part of the story as well.
Not entirely. 'The Keepers' likely takes inspiration from real incidents but incorporates fictional aspects to make the story more engaging and compelling.