Originally published in 1926, The Murder of Roger Ackroydremains a classic of crime fiction. Written early in her career, this was the third novel to feature the Belgian detective Hercule Poirot. (Goodreads list this as #4 in the series, but most other sources have it as the third.)
The book takes place in the small English village of King's Abbot, and opens with the death of a widow named Mrs. Ferrars. Rumors quickly spread among the villagers that she has committed suicide and that she had earlier murdered her husband by poisoning him. Following the death of her husband, she has also been rumored to have been carrying on a secret relationship with Roger Ackroyd, the wealthiest man in King's Abbot.
That same night, Ackroyd is found murdered, stabbed to death in his study. Ackroyd's family and staff had been instructed that he did not wish to be disturbed that evening and when his body was discovered about ten o'clock that night, the door to his study was locked from the inside. A study window was found open, and muddy boot prints suggest that someone entered and left the study by climbing through the window.
We learn all of this from the story's narrator, Dr. James Sheppard. the quiet country doctor who attended Mrs. Ferrars and who is a close friend of Ackroyd's. Ackroyd is distraught by the woman's death and asks Sheppard to visit him that evening. Ackroyd is burdened by a terrible secret that he reveals to the doctor. In fact, Mrs. Ferrars hadpoisoned her abusive husband and had confessed her secret to Ackroyd the day of her death. Ackroyd now fears that the woman may have killed herself because of his reaction to her confession. Sheppard counsels Ackroyd and then leaves the house a little after 9:00. A little less than an hour later, Sheppard gets a phone call which sends him racing back to Ackroyd's house. He and the butler break down the study door and find Ackroyd dead.
There are any number of potential suspects, including houseguests, family members and the large household staff. Several of these people are having money problems; most of them are in Ackroyd's will and will be financially better off now that he's gone.
The local constable is clearly not up to the task of sorting this out and finding the killer. Fortunately, the renowned detective, Hercule Poirot, has recently retired and is living quietly in King's Abbot, growing vegetable marrow. He agrees to be pressed into service and begins an investigation with the good Dr. Sheppard at his side, chronicling the investigation in the manner of Dr. Watson, or of Poirot's old friend, Hastings.
This is, basically, the typical English manor house mystery raised to classic status by the brilliant design of the plot. Even early in her career, Christie was a master of setting a book like this in motion, giving the reader all of the necessary clues, and then daring them to divine the solution before Hercule Poirot could reveal all. If you're only ever going to read one novel by Agatha Christie, it should be this one, and even if you're not a fan of this sort of mystery, it's one that any fan of crime fiction should certainly have read.