When I was a nipper I used to go into John Menzies, pick up an Agatha Christie with an intriguing cover, and see how much I could get through before the staff started sniffing around. I must've read at least the first few chapters of quite a few that way.
I think this could've been one of those, because I remember the set up well, but not the denoument. It's the first Miss Marple novel, and I do marginally prefer her to Poirot, though they're both pretty great. It has the classic opener - kill off the most detestable character whom everyone's got a beef with. Then throw in some red herrings, then a few reverse red herrings. By the end your head's buzzing, but the solution was right on front of us all along. Of course.
What I always like in these books is the attention to detail in the plotting. Things are revealed in the correct order and at the end it's like a clockwork apparatus with everything in the right place. Realism isn't the goal, but strict internal consistency. But it's Christie's view on human nature which is the secret ingredient. She seems to understand what drives people, whether to love or to murder, and I always find the characters interesting and convincing. She also has a dark sense of humour, and understands that a passion for murder, which she shares with her readers, is perhaps a little unhealthy.
Not my favourite of her books, but I've got plenty more for the kindle now when I want the literary equivalent of a KFC. Hmm, now I want a KFC.