#243 at time of writing.
This film was like an Agatha Christie novel - very clever, and quite satisfying, but not particularly deep, and populated with fairly stereotypical characters.
Hitchcock manages to keep the suspense and intrigue going throughout, as is his wont, but I disgree with all the people that say he is a master of the medium. He doesn't use the versatility of film to its full extent at all - he produces films that feel like stage plays (at least the ones I've seen).
That style doesn't sit easily with me, it makes me restless. So although this is a perfectly good film, with some surprising twists, I wouldn't rank it among my favourites.
Bizarrely, this was originally filmed in 3D, which explains the prevalence of low-angle shots with lamps and other objects in the foreground. There was only a brief original release in 3D, followed by a conventional "flat" release; the 3D version was reissued in 1980.