Agatha Christie mentions this as one of her best novels in the forward. She describes the characters as being complex and hopes the users enjoy it as much while reading as she did when writing. 
 I did not find the introduction to Charles and Sophia very interesting. When they meet some 2 years later and Charles suggests they marry Sophia is hesitant as her grandfather has recently passed and the police suspect it's murder. Now it would have been possible for the author to write that Sophia agrees and then continue the investigation but I like how Agatha Christie points out how it would reflect on Charles, a diplomat, and on the visa issues they would face if the case is never closed or the police catch the wrong person. 
 Now in like all her novels every person is a suspect. Some more than others. The gradual reveal of each person's motives and the story progression is really good. Also I felt this novel had a lot more background on the victim than any of her other novels (at least out of all the ones I have read). 
 One is left guessing till the end as to the perpetrator. I found the ending a tab bit disappointing. (view spoiler)[ What with Aunt Edith taking the blame on herself and then driving Jospehine and herself off the cliff because she does not want the child to suffer (hide spoiler)] 
 A solid 4 stars.