Christie still has it, the ability to bewilder and amaze, at age 79! She shows herself capable of making poignant and truthful observations, throughout the book, about youth, the changing state of society, and of course, the mind of those capable of crime and murder. I am always facinated by the amount of quotable quotes in any Christie novel.
It is true that some later Christie novels are not quite as palatable as her earlier work, but this is simply not one of them. As fresh as her first works, with a believable ending and a incredible and intriguing motive for one of her characters, I'm wondering how anyone could read this and not see the value. Christie shines when she takes out Poirot, and the duo of Oliver and Poirot is a treat.
The only flaw I see here is Christie's inability to see 'lower class' servants as capable of being worth as much as the upper classes, but she was a Victorian, and raised with prejudice. Still, the continual references in her books to servants who morbidly get excited about death, who are stupidly superstitious, who cannot make inferences, or in short behave like common sheep get to be wearing. Christie is also racist; Frenchwomen, Englishwomen, Americanwomen, and those from the 'colonies' are highly bred and of good bearing, but those from Spain, Italy, and other 'ethnic' countries are too often dismissed in a single sentence and described as having 'a simple good nature and flashing teeth'. Ouch. I won't even go into how she describes Arabics.
So long as you can view her work for what it is, a excellently crafted, yet lighthearted murder mystery, written by an Englishwoman born to priviledge, who lived in somewhat of an ivory tower, you will be able to enjoy.