I wasn't overwhelmed by the characters. Perhaps it is that our main character, Winter Musgrave, is part-amnesiac and terrified through the first third of the book, but it was very difficult to get comfortable with her. Once we have some idea what is happening to her it is easier to dig in. I think that MZB has an interesting premise with this one, and I think the "why" of the mystery is well thought out. However, (note: I am trying to avoid any spoilers, otherwise this might be more coherent) I think Winter's eventual visit to her family serves only to introduce characters for another novel and doesn't seem structurally significant, and the ending did not satisfy.