The story involves ten people invited to an island under different pretenses. Once there, each guest is accused by a mysterious voice on a gramophone record of committing a particular murder. Then the guests themselves begin falling prey to a murderer. After each killing, a soldier (or Indian) figurine from the dining room table is broken. In each of their rooms is hung a copy of the nursery rhyme "Ten Little Soldiers" (or "Ten Little Indians") and the murders eerily echo the verses of the rhyme. If they are alone on the island, then the murderer must be among the ten of them, but who?
Christie herself adapted the novel for the stage, changing the ending significantly (basically, injecting a form of a "happy" ending). I was interested in reading the book to compare the two, and my curiosity extended to my viewing two film versions, Rene Clair's And Then There Were None (1945) and George Pollock's Ten Little Indians (1965). In terms of the story, I thought the book was the best, followed by the 1945 film version, the 1965 version, and finally the play. The problem with the play was that it did not spell out certain things that the movie versions did fill in. Ten Little Indians is inferior to the 1945 film for several reasons: the setting is changed to an Austrian mountaintop; some of the characters, their alleged crimes, and how they are killed off are changed (and not for the better); there are too many gratuitous shots of Vera undressing; and it seems too dated to the 60s.
Overall, though, the book cannot be beat. What I most appreciate about it is the "note found in a bottle" postscript. It explains everything from the murderer's point of view. And Then There Were None is an extremely clever mystery!