Agatha Christie is one of the rare writers who has completely transcended pop culture to become a more or less permanent fixture in the literary filament. Most authors — even best-selling authors who won awards and enjoyed huge sales of their books — fade away shortly after they die, their work falling out of fashion. A favorite example is George Barr McCutcheon, who had several bestsellers in the early 20th century — including "Brewster’s Millions," which has been adapted to film seven times — and was quite the literary star. A hundred years later, few people know his name, and if they know the title of his most famous work, it’s probably because of Richard Pryor.

But Christie is something else entirely. [...] Christie’s works are protected from the sort of rot that makes most non-literary classics fade from the public mind, of course, because they are generally quite clever, and the mysteries they describe and solve are crimes and schemes that could still be attempted today despite the march of time and technology. That makes Christie’s stories very adaptable, and indeed they are still adapting her most famous novels for television and film. Whether as period pieces or with effortless updates, these stories remain the gold standard for a “whodunnit.” On top of that, despite being a writer of paperback mysteries, a traditionally low-rent genre, Christie injected a certain thrilling literary adventure into her writing, ignoring the rules quite often and setting new standards [...].

And that’s likely the reason for Christie’s continued popularity. Despite writing what could have been tossed-off novels that sold like hotcakes and were then forgotten, Christie managed a perfect balance between intelligent artistry and the red meat of surprise twists, sudden reveals, and convoluted murder plots. Tha t literary intelligence, in fact, means that there’s a lot more than just clues to the mystery at hand in Christie’s stories — in fact, there are clues to Agatha Christie herself hidden in her prose.

(Adapted from: https://www.thoughtco.com/agatha-christie-secrets-4137763)