Appointment with Death by Agatha Christie (1938)

Agatha Christie created 2 fabulous characters - Hercule Poirot, and Miss Marple; each of them were brilliant at connecting clues, tying them in with human emotions and solving crimes that would baffle other people; in that respect, they were similar to Sherlock Holmes (created by Sir Arthur Conan Doyle). Hercule Poirot was made as a lovable, and yet highly vain character. He knows that he is smart, he can solve cases that no one else can, and he is very vain about his moustache. He is also a perfect gentleman in terms of manners, although with a high ego, he can get easily offended. All these characteristics pale in front of the indisputable fact that he can use clues to evolve a story, change his thinking if the clues don't match, and explore all possible alternatives even if they seem extremely unlikely.



This particular novel, 'An Appointment with death' was released after many other Hercule Poirot stories had been published, so the standard for Hercule Poirot in terms of character and success was already set. Here was a guy who read the same clues as the reader, and others in the story, and yet was able to solve the crime (in many cases, the actual murdered was a surprise to most people - read 'Murder on the Orient Express' as another great book with the same subject).
The novel deals with a family under great stress, the matriarch of the family is a tyrant of the highest degree, controlling the family (interactions, emotions, experiences, she controlled everything). This stifling was causing immense harm to the family members (including possibly breaking up the marriage of her son), and then, while on a trip to the Middle East, she is murdered. There is not much time to solve the crime, and since Hercule Poirot was at the same location, his services were requested. He needs to figure out the various movements, marshal the clues, and see which of the oppressed family members committed the crime.
The initial part of the story where the family is getting discussed between 2 outsiders, Sarah King and Dr. Gerard, is fascinating as you get to understand the family dynamics in fair detail. This is setting the ground to claim that most people in the family also had a reason to kill her, and then Poirot had heard something earlier that seemed like her children were plotting to kill her. In the 24 hours in which he was involved in the case, he works out that the family members had indeed found her dead, but suspected the other and hence tried to save them.
The name of the murderer, when finally revealed, is a major surprise, one which most readers would not have predicted.