Most King books have been adapted for the screen or TV. There is still a group that hasn't.
For the record, here they all are:
Rage
The Long Walk
Roadwork
The Dark Tower series
The Talisman
The Eyes of the Dragon
Gerald's Game
Insomnia
Rose Madder
The Regulators
Bag of Bones
The Girl Who Loved Tom Gordon
Black House
From a Buick 8
Cell
Lisey's Story
Blaze
Duma Key
Under the Dome
Or, perhaps, even some short stories or novellas, of which there are a sizable amount.