The Haunting of Toby Jugg is a masterpiece. I have frequently cited it as the scariest book I've ever read and I stand by it. The first time Toby hears the "Devil's" rapping at his window is a masterclass in how to write suspense. The atmosphere, the mounting sense of insanity and evil, all of these things are handled so well throughout the novel, I still find myself breaking out in a sweat even writing about it.
I'd forgotten Dennis Wheatley's novels, he's been out of print so long. Now his novels are being reissued -- and they're on Kindle.
What fun. :-)