I honestly really love her novels. Sometimes they're a bit contrived, but they're fun and somehow not as dull as other murder mystery novels that I've tried to read. I can zip through one of her books in 4-5 hours.
Here is a great podcast about her: https://podcasts.apple.com/nz/podcast/185-agatha-christie/id...
She died in 1976, so in life+50 countries, all her works will become public domain in 2027 (84 will still be copyrighted in the US); in life+70 countries, the year will be 2047 (34 will still be copyrighted in the US). The copyrights will continue to expire in the US until 2072, when the the last book published in her lifetime falls into the public domain.
Note that this "study guide": https://www.studymode.com/essays/And-Then-There-Were-None-My...
gets the name of the island wrong: it's "Soldier Island."
For obvious reasons, that title was considered unsuitable for sale in America, so American editions were renamed to And Then There Were None, and the island and poem were changed to reference (depending on edition) Indians or soldiers instead. Most editions these days have settled upon soldiers.
Incidentally, Wikipedia mentions one use of the phrase “our black brothers” that only makes sense in the context of the original naming.
Perhaps they mean "Vera Claythorn becoming semi-hysterical" only makes sense knowing the name, but that's a bit of a stretch.
Whilst there are several islands off the coast of Devon, hers was a fanciful creation. The entire story just revolves around poem.