I read On Writing just recently and thought it was a very helpful and cogent book on the writing process, it gave me a lot of valuable insights for my own writing. I had to square how insightful the book was with the fact that it's King writing it, who's writing I've never cared for much. It has been awhile (decades) since I read any of his stuff, but I suspect that much written in On Writing is advice he probably doesn't strictly follow writing his own books. Still a good book nonetheless. King is an odd duck, that's for sure.