Update: Finished it at around 11h30. Liked it very much and totally recommend it. I still prefer Christie's And Then There Were None. I think they're very different, the only similar thing is the idea: people are invited to a place and then... :-)
But the two books make things work quite differently. I recommend both and *if* Christie saw the film, they're both an example how the same idea can have different developments.
We went out to lunch, took some calls and now onto the Black Coffee.