Black Coffee by Agatha Christie (adapted by Charles Osborne)

It is 1934 and Sir Claud Amory has invented a formula for a very powerful weapon.  World War I is in the past and the second hasn't yet begun, but some can see the signs of what is to come.  Hence the formula is considered quite valuable and important.  Sir Amory fears someone in his household is trying to steal the formula so he calls on famed detective Hercule Poirot to investigate, but before Poirot even arrives Sir Amory is murdered in the library.

Black Coffee is what I call a puzzle mystery.  Some mysteries are like a treasure hunt.  The hunt begins at the crime scene and the reader/detective doesn't know where he or she will have to go before reaching the end and solving the mystery.  In contrast, in a puzzle mystery there is a contained space with a finite number of suspects and all the necessary clues.  There is no need to go anywhere else.

Agatha Christie is one of my go-tos when I want to read something quick and fun, but that will also make me think a little.  This is not one of Christie's best stories.  There are a couple obvious suspects in the beginning, so obvious that I knew that I knew neither could possibly be the murderer. Still I enjoyed it.  For a better Christie mystery, try And Then There Were None, The Man in the Brown Suit, and of course, Murder on the Orient Express.

Random Bibliographical Fact: Black Coffee was Christie's first mystery play.  It premiered on a London stage in December 1930 and was later adapted as a novel by Charles Osborne.