Just finished it and I loved it. I remembered seeing the theatrical version of this do, also written by Christie but with an altered ending at the Red Barn Theatre on Lake Simcoe with my mother when I was much younger. I had, however forgotten the ending thus allowing the novel to be as tense and grim as it was intended to be. I was surprised by the ending and later debated it with my wife (also a fan of Christie). My wife finds this novel far too gloomy and the end unsatisfactory. I had to agree that though in hindsight the foreshadowing is all there it is only with the explanatory letter that all becomes clear, and there are a few far fetched circumstances. Nonetheless I think it is a masterpiece in its genre. According to one source I found, it is the seventh most popular novel written. The book itself I chanced upon at a summer garage sale in Toronto and purchased it for about 50 cents. Money well spent.