I have of course read this earlier, but have re-read it for discussion with my U3A Agatha Christie Reading group. I think they will enjoy the read. I think this is one of the best Marple stories.

Despite the advice not to investigate Gwenda and her husband decide try to work out what Gwenda's vague memories of the house she has recently bought actually mean.

I particularly liked the description of Miss Marple.
Miss Marple was an attractive old lady, tall and thin, with pink cheeks and blue eyes, and a gentle, rather fussy manner. Her blue eyes often had a little twinkle in them.

There are no signs that this was actually written during World War II and stored for later publication. Certainly no signs that it was meant to be Miss Marple's last case. ( )

Miss Marple's Last Case?
Review of the William Morrow Paperbacks edition (August 23, 2022) of the Collins Crime Club (UK) hardcover (October 1, 1976) & the Dodd, Mead & Company (US) hardcover (late 1976) originals.

"After eighteen years, you and Giles come along, asking questions, burrowing into the past, disturbing a murder that had seemed dead but was only sleeping … Murder in retrospect … A horribly dangerous thing to do, my dears. I have been sadly worried."

Sleeping Murder has Miss Marple helping Gwenda and Giles Reed, newlyweds who have moved into a new home in England after living abroad. Gwenda begins to have déjà vu feelings in the house as if she had witnessed a murder there. She also has memories of various doors and structures in the house. It gradually dawns on her that she had lived in the house in her childhood and that the murder recollection must be real. She and her husband set out on a dangerous course to uncover the murderer after many years.

See cover at https://upload.wikimedia.org/wikipedia/en/3/36/Sleeping_Murder_First_Edition_Cov...
The front cover of the original 1976 Collins Crime Club (UK) hardcover edition. Image sourced from Wikipedia.

On the Berengaria Ease of Solving Scale® I found Sleeping Murder to be on the high end i.e. an 8 or so. There were too many suspects and possible motives. You could perhaps make the leap to the solution by asking yourself "who is the unlikeliest of the characters to be the murderer?"

Confusion for Completists
Although it was the final published Miss Marple novel in 1976, Sleeping Murder is actually estimated to have been written between the years 1940-1944. You can read that background in the Wikipedia article linked above. It was followed in 1979 by a further posthumous collection in the UK Miss Marple's 6 Final Cases and 2 Other Stories, although those short stories had appeared earlier in the U.S.

Trivia and Links
Sleeping Murder was adapted twice for English language television series. The 1987 BBC version is faithful to the original. The 2006 ITV version adds new characters and subplots to the story. I did not find any free trailers or postings of either of them, but they are both available on the Britbox streaming service here in Canada.

The first TV adaptation was as part of the BBC's Miss Marple (1984-1992) series as Episode 6 in 2 parts in 1987, which starred Joan Hickson as Miss Marple.

The second TV adaptation was as part of ITV's Agatha Christie’s Marple (2004-2013) reboot series as Season 2 Episode 1 in 2006 which starred Geraldine McEwan as Miss Marple. ( )

Luettelosta poiketen suomeksi

Interesting

First one I’ve ever properly guessed the killer early on. Normally she stumps me. But very clever and well done all the same. ( )

I've just come to expect so much from a Christie novel... so, what was a perfectly adequate mystery feels like a bit of a let-down. The pace was kind of plodding, and the solution doesn't come as much of a surprise by the time you're there. It seems like most people love it, though, so who knows! ( )