I think it's aimed more at teens than kids, it was one I read when I was a kid and it terrified me.
The cover I remember, but not hte name or author.
The cover (I think) was pale blue with pastel door frames on it, one inside the other. It was a bit of a post apocalyptic story, that gave me nightmares, and I've grown up hooked on horror, so it's always stuck in my head and I'd love to know what it actually is. Any ideas?