Agatha Christie's book (originally titled, in the UK, as 'Ten Little Niggers', in accordance with the terminology of the time - this was after all 1939.) has a completeness and subtlety of plot which the BBC can for some reason never achieve. Every time the BBC dramatises a classic (Austen, Dickens, Conan Doyle.) it should have, just under the title, the words 'Loosely based on an idea by' - as a kind of caveat. It is, in the final analysis, typical BBC.
There is a lack of understanding in this film of the original plot, which is not only fatal to the interpretation but is actually quite horrible.
The only thing missing was Agatha Christie's brilliance.
The house, the cast, the pathetically fallacious cloud formations, sunsets and dramatic weather, the costumes, hair and makeup taking each character from groomed control to dishevelled à la Marat/Sade - everything contributes to this brilliant psychological drama of Agatha Christie at her finest. The title sequence alone deserves an Oscar, with those beautiful jade figurines disintegrating and morphing into a model of the island where it all happens. This is certainly the best 'film of the book' there has ever been - so far.