When I was in my teens, Christie was my favorite author, and I read most of her novels and short stories. Going back to them a few years ago, I was struck by the viewpoint of everything through a very prejudiced higher class white English lens, and how poor some of the writing is, particularly in terms of characterization.
But her plotting of the central mystery, by and large, is impeccable and airtight. Something like what dramedy states wouldn't really happen in a Christie novel.
To bring us back on topic, the only Christie plays I've seen are local productions of The Mousetrap and And Then There Were None, the latter of which was kind of botched by the local company. The way it was staged, the murderer had to be in two places at once or the fastest human alive.
Interesting that both And Then There Were None and Witness for the Prosecution have different endings than the original source material. I think The Mousetrap is basically the same.