I have not been scared by SK's books, but that's just because I really find them interesting and want to know what happens next (I have trouble putting them down), but when I close the book, I keep thinking about the cool story, not about things that happen in the book suddenly happening outside of it, too.
But I think this book would be hard to read if I had children. In other books, I can try to imagine the story happening to me. But with this one, this is something that one would not want to happen, not even pretend it or imagine it.
There is one thing I noticed about this book since the start, which is obvious from the title, but pretty evident when one starts reading. The focus on death is too strong, even from the first sentence. I think of my boyfriend, who really reminds me of Rachel. He totally hates even speaking about death. I cannot mention things like "when I die" because he shuts me up. He does not want to imagine that death is something natural (as Louis repeatedly says) and that it is coming for all of us. I believe he would be frightened by the book even before the cat is neutered.