Frightening Non-Fiction Recommendations

I've spent ages reading horror and not really being effected by it. Like I can feel repulsed by something grotesque, or intrigued by characters in horror.. but horror doesn't really frighten me.

I have leaned more towards hard science-fiction because I suppose the potential plausibility tends to frighten me more. For just one example, Seveneves, I found especially frightening. In movies, too… as a kid, I was more frightened by the movie Deep Impact than I was by Poltergeist.

And that got me to thinking… what books have truly frightened me? Superintelligence by Nick Bostrom, The Hot Zone by Richard Preston, Nuclear War: A Scenario by Annie Jacobson.

So suggest me some truly frightening non-fiction books based on what I've outlined above.