The scariest works of fiction I have ever read are
Red Dragon and
The Silence of the Lambs, both by the wonderful must-make-him-a-saint-one-day Thomas Harris.
Tragically, however, the scariest books I have ever read have all been non-fiction. Any book about North Korea, for instance - there are a few good ones, but I would say that
Nothing To Envy by Barbara Demick and
The Aquariums of Pyongyang by Kang Chol-Hwan are probably the best. And, as a special personal recommendation,
The Good Women of China by Xinran Xue. Xue was the first journalist in communist China to be allowed to cover women's issues, and she travelled all over China interviewing women from party cadres to housewives to illiterate labourers to students and teachers, and asking them about their experiences of living in a brutal and deeply patriarchal dictatorship.
The Good Women of China is a collection of some of her most memorable (in other words, the most heartbreaking, outrageous and unjust) encounters... She is a superb, perceptive and intuitive interviewer and a marvellous prose writer, and the result is... Well, the result is the saddest and the most moving book on my shelves by a country mile. You
will cry, and you will rage, and you will thank the Lord you were born where you were.