Agatha Christie is one of the most successful authors of all time, selling into the billions (yes, billions) detective mysteries starring unassuming heroes such as the sweet but cunning Miss Marple, and the small but indomitable Hercule Poirot. 
Unlike the easily comparable Sherlock Holmes (Written by *Arthur Conan Doyle|/authors/arthurconandoyle*), Christie claimed that Poirot was a little less super and more human. Poirot is indeed often more focused on analysing the character of his suspects and deducing the motives rather than specks of dust and fingerprints. He also exhibits a slight (albeit rare) humility in his abilities that the famous Holmes would never admit.
Christie’s mysteries are often set in high society, with the clients often holding much gravitas as actresses, lords, academics and ministers—or at least being extremely rich. They are set in manors, hunting lodges and of course trains and cruise-liners.
While most of her works are still copyrighted, some early short stories have fortunately made their way into the public domain. These Poirot mysteries are short and snappy but soaked with intrigue, and full of twists and scandals. May I suggest you begin with a blackmailed actress, a mythical prophesy, and a scream in the dark, all to be found in * The Adventure of “The Western Star”|/onlinereader/the-adventure-of-the-western-star*.