I don't think I realized when I read this book many years ago as a teenager just how much of a homage to Arthur Conan Doyle it is. There are obvious parallels between Holmes and Poirot, Dr Watson and Hastings, and Inspector Lestrade and Superintendent Japp.
I do enjoy it when Hercule Poirot gathers all the suspects in the drawing room and then proceeds to unmask the murderer. I'm sure there isn't an ounce of legality in it, but it's a heck of a lot of fun. However, the casual anti-Semitism, overt snobbery and racism is a bit hard to swallow.