Agatha Christie publishes Sleeping Murder
Christie wrote Sleeping Murder and Curtain during World War II to be published after her death, Sleeping Murder was most probably written during The Blitz in 1940.
However, unlike Curtain, which concludes the career of her other famous detective Hercule Poirot, there is nothing in the text of Sleeping Murder which indicates it is Marple's last case. Both books were sealed in a bank vault for over thirty years.
The last Marple novel Christie wrote, Nemesis, was published in the 1971, followed by Christie's last Poirot novel Elephants Can Remember in 1972 and then in 1973 by her very last novel Postern of Fate. Aware that she would write no more novels, Christie authorized the publication of Curtain in 1975 to send off Poirot. She then arranged to have Sleeping Murder published in 1976, but died before the publication.