I totally failed to guess the killer!
Poirot was staple TV viewing when I was a teenage so the image of the character is burned well into my consciousness (thank you David Suchet) - so reading an Agatha Christie book tends to come with very easy imagination and even accents for characters.
The story is well built, told in a way that makes me think I should have been able to deduce the killer myself (and something I've always wondered about murder mystery stories) and does a good job of flipping my expectations on its head!
Solid stuff.
Others I've read in the "Hercule Poirot" series: