Horror legend Stephen King has already seen the new It movie twice and says he was "not prepared" for how good it is.

The author penned the book the film is based on, along with several other adaptations including The Shining, Carrie, The Shawshank Redemption, Pet Sematary, Stand by Me, Misery, The Green Mile and The Running Man.

King's It had already been adapted for the screen with a 1990 mini-series, but the new scary clown movie has really impressed him a great deal.

"I had hopes, but I was not prepared for how good it really was... I went back and saw it a second time, and I felt I was seeing things the second time through that I missed the first time," he tells Bloody Disgusting.