King posted a letter to his readers on his website announcing the latest installment:
Dear Constant Readers,
At some point, while worrying over the copyedited manuscript of the next book (11/22/63, out November 8th), I started thinking—and dreaming—about Mid-World again. The major story of Roland and his ka-tet was told, but I realized there was at least one hole in the narrative progression: what happened to Roland, Jake, Eddie, Susannah, and Oy between the time they leave the Emerald City (the end of Wizard and Glass) and the time we pick them up again, on the outskirts of Calla Bryn Sturgis (the beginning of Wolves of the Calla)?
There was a storm, I decided. One of sudden and vicious intensity. The kind to which billy-bumblers like Oy are particularly susceptible. Little by little, a story began to take shape. I saw a line of riders, one of them Roland’s old mate, Jamie DeCurry, emerging from clouds of alkali dust thrown by a high wind. I saw a severed head on a fencepost. I saw a swamp full of dangers and terrors. I saw just enough to want to see the rest. Long story short, I went back to visit an-tet with my friends for awhile. The result is a novel called The Wind Through the Keyhole. It’s finished, and I expect it will be published next year.
It won’t tell you much that’s new about Roland and his friends, but there’s a lot none of us knew about Mid-World, both past and present. The novel is shorter than DT 2-7, but quite a bit longer than the first volume—call this one DT-4.5. It’s not going to change anybody’s life, but God, I had fun.
— Steve King