Bobby Roberts
Banned
From what I recall, King started writing It in 1981 and finished, I believe, in 1985. The novel was released in 1986 and he was probably starting Tommyknockers either before he finished It or right after, and the fact that he was said to be high during the filming of Maximum Overdrive (also 1986), it's likely he was high sometime during the writing of It.
I believe the writing of Tommyknockers was actually interrupted by his family doing an intervention.
So that book was not only him drunk/high as fuck, but also him detoxing as well.
(it's probably his worst book, too)