This is a question that a BookEnds asked: http://www.nytimes.com/2014/10/26/books/review/whats-the-most-terrifying-book-youve-ever-read.html
The writers chose books for various reasons, including how real the book felt.
He who controls the past controls the future. He who controls the present controls the past.
For me, the scariest book I ever read is Nineteen Eighty-Four. It’s dystopian, not horror, but the way they changed the newspapers after publication? Yeah. Not taking it back, not apologizing for a print error, but changing it altogether.
That kind of thing wasn’t possible when it was written, it wasn’t possible in 1984, but it is possible now. And that’s scary.
I love ebooks and reading online in general, but that kind of thing is possible and it scares me. It really does.