Agatha Christie wrote sixty-six mystery novels over the course about fifty-six years. The world changed in the course of the those fifty-six years. As a teenager, getting a smattering of impressions from different points in those years, in no particular order, was sometimes startling and even a little sad.
Over that entire span of time there were always elderly people who complained about how times had changed, but at the end you could feel that they really had. Even with less stringent definitions a ‘proper housemaid’ made fewer and fewer appearances, and while young people might gallivant around solving mysteries in any era, they moved from nudging at boundaries to barely being aware earlier boundaries had existed. The feel of the entire world changed.
And yet, however much the feel of the world changed, the bones of it never did. From beginning to end of Agatha Christie’s stories, proper housemaids or no, people fall madly in love, do crazy stupid things that sometimes end well and sometimes end very badly indeed, eavesdrop on strangers, ignore close relations, throw parties to impress distant acquaintances, poison elderly aunts, bludgeon rivals, and sometimes drop everything and risk their lives to prevent the murder of another human being.
As a teenager I might have a grasped in a distant sort of way the concept that times change but human nature remains the same. In Agatha Christie I saw it happening, and never even knew it might be profound.