A murder disrupts a quiet train ride, leaving passengers to defend their innocence in the trailer for ‘Murder on the Orient Express.’

“Murder Is Easy,” Agatha Christie once proclaimed, as she dreamed up the title for one of her classic crime novels.

Easy for Dame Agatha, anyway.

In 2017, the British “Queen of Mystery” (as her current publisher has dubbed her) is having a moment, yet again. The novelist and playwright, who had a pretty good run during her lifetime (1890-1976), is hotter than ever in the 21st century.

The “Queen” indeed reigns over a publishing empire, with two new movies out this fall (Murder on the Orient Express and Crooked House), a series of TV adaptations set to stream on Amazon, and books on current best-seller lists thanks to a complete reissue of all her mysteries in the U.S. and a new series of Christie novels being penned by contemporary crime writer Sophie Hannah.

Why does the creator of celebrated sleuths Hercule Poirot and Miss Marple — who has sold more than 2 billion books worldwide, outranked only by the Bible and Shakespeare — still knock ’em dead nearly a century after she published her first book?

Let’s examine the evidence.

She wrote murder, folks

It starts with the books, of course. And in the 21st century, the image of Christie as a sweet old lady who wrote quaint tales of gentle deaths (often by poison) set in charming English villages is shifting to a more nuanced view. Christie 2.0 is studied at academic conferences and in scholarly books, with a new generation of mystery writers piping up as vocal fans. Agatha Christie, a hack? Prove it, they say.

“She’s the gold standard, the Shakespeare of crime writers, and she influenced many, many of today’s crime writers,” says Hannah, a British mystery novelist (Keep Her Safe) chosen by the Christie estate to conjure up new Poirot mysteries (2014’s The Monogram Murders and 2016’s Closed Casket, with another title coming in 2018).

Hannah believes Christie in the past was underrated by “snobby people” who thought she was a page-turning “genre writer,” while Hannah trumpets her mentor as a serious literary stylist who combines “brilliantly strong storylines with truths about human nature,” among them greed,…