It started life as a short story on social media, but Slade House is now set for publication in October 2015, the month in which its fictional conclusion takes place.
Mitchell had originally distributed The Right Sort as a collection of 280 tweets, commencing on July 14, 2014.
But, as explained in a joint statement with publisher Sceptre, it quickly acquired a life of its own as scenes grew, bred and sprouted new scenes.
Eventually, The Right Sort became the first of a five-part novel that will see the light of day as Slade House.
With Mitchell's readers accustomed to seeing new work arrive every two years, and The Bone Clocks released only last September, the new work breaks with established convention.
But, inhabiting the same fictional world as his most recent novel, a swift production process for Slade House is not necessarily inappropriate, with Sceptre teasing the appearance of a character who might be a shade familiar from The Bone Clocks.
"Slade House is on a shorter scale than his major novels, but is every bit as enthralling and inventive," said Sceptre publishing director Carol Welch, describing it as a taut, spine-chilling, intricately woven, reality-warping tale that begins in 1979 and comes to its electrifying conclusion on October 31st, 2015.
The Right Sort can be read in its original form at: twitter.com/sceptrebooks/timelines/488586138048004096