And Then There Were 56: The Sittaford Mystery by Agatha Christie

Well, this turned out to be rather a delightful read, despite a
surprising number of unpleasant characters of the male persuasion.
Perhaps that is the ultimate revenge of our plucky heroine, Emily
Trefusis (not to mention Dame Agatha herself), in this, our very
first standalone novel. So make yourself a hot cocoa (sans
strychnine, please) and come enjoy with us the wintry wonders of
Devon....