I adore Agatha Christie's writing, so even if this book is not my favorite of her mysteries, I still enjoyed it.
Agatha Christie was not a technically brilliant writer -- She never claimed to be. But where she is unmatched is in her study of human nature. She knew that people will say one thing, and project an image one way, and could be almost entirely opposite of what they were saying or projecting. She could see the cracks where the "real" person could be glimpsed. And she could write her characters so that they projected an image that was contrary to their true nature. Her detectives could, and close readers can, always see the cracks, and that is how the mysteries are solved. The clues are all there, but don't expect her detectives to point them out to you along the way. The ending with either surprise or validate you, depending on how closely you read the story.