Call me daft, but i really really like this Christie novel.
The characters are great (especially the sublime Mr Satterthwaite, and the wonderfully entertaining Hermoine "Egg" Lytton Gore). Really entertaining, and great to read about. As with many of the best Poirot novels, Poirot himself does not really take a large role until quite a way ino the book ("Appointment With Death" "Cat and Among the Pigeons", for example.)
The plot is great, and the motive for the first motive is just sheer originality. (Even though it, and the motives for the other murders, is just a tiny weeny bit thin).
It's a pretty light Christie book, but with a brilliant first death and motive for it. And a great, rather unexpected solution. It may not be her very very best novel, but it is still one of the great ones.