The Guardian reports:
The collection, titled Marple, marks the first time anyone other than [Agatha] Christie has written “official” (as recognised by the Christie estate) Miss Marple stories. The 12 women who contributed to the collection include award-winning crime writers Val McDermid and Dreda Say Mitchell, historical novelist Kate Mosse, classicist and writer Natalie Haynes and New York Times bestselling author Lucy Foley.
(If the Guardian link above doesn’t work for any reason, here is an alternative link from Smithsonian Magazine quoting The Guardian.)