However. Preserve me from the "lower-class" characters in Christie, particularly the servants. They're not even human. (I once mentioned this to an acquaintance, who argued that the "Oh, ma'am" simpering servant-girl was accurate for the time. Maybe in front of Ma'am she was--I'm sure she didn't want to lose her job--but the characters behave with equal slack-jawed imbecility when there's no one around to pretend to.)
I'm not going to hold this classism against Christie too much, because (a) she was obviously a product of her time and place, and (b) she was obviously writing stock characters, so it's unfair of me to complain about her writing stock characters.
Also, it's too late now to change her attitudes, if any.
But it's worth noting that at least two of her contemporaries, Ngaio Marsh and Patricia Wentworth, did a much better job at presenting working class characters as real people. I always used to wonder if the fact Marsh was a New Zealander was a factor in that. I have no idea how to explain Wentworth. Except that I think she also wrote romances, which are carried by characters rather than the strict puzzle plots Christie excelled at. Maybe that was it?
And now it also occurs to me that Christie also wrote romances as Mary Westmacott (I haven't read any of them) so that probably isn't it, either.
Perhaps I'll chalk it up to "different writers are good at different things."*
*Edited to add: By "different writers are good at different things," I mean that Wentworth and Christie wrote at about the same time, and in the same genres, and Wentworth is far better at creating characters. I know very little about Wentworth as a person or what social class she belonged to, but as neonorne points out below, it's possible Christie's problem was not so much that she couldn't write characters, as that she couldn't see the "servant class" as people. Maybe Wentworth was just better at seeing people as people, or maybe there were reasons she could. I've read Christie's biography but not for years, so I can't even guess which interpretation is likelier to be true.