I read this book when it first came out, I think I still have it somewhere.
I'm stealing from a few of the earlier comments as some of them made me remember the book quite clearly.
Yes good development of the characters because after all this time I
remember them and how they related/interacted with each other.
And yes I remember that sense of foreboding, the tension, and my uneasiness and irritation with Dr. Faraday. I remember it was one of those books where I kept saying oh just a few more pages and a few more, then the next thing I knew it was 2 in the a.m. She's good enough
that I searched out the rest of her books. She's good enough that I remembered the feeling of the book
years later. The words used in the other comments are right on, foreboding, dread, tense and disturbing.