Hitchcock outdid himself on this early work. I thought his entire adaption of the novel was fascinating. The story itself is way ahead of its time, at least as far as cinema goes. (Theatre is a different story.)
What impresses me most about 'Murder!' is that its characters are so rich, so easily defined, so unique, so perfect. That's unusual in a Hitchcock film. And beyond that, the acting is supreme. At night, when the characters are tired, they actually yawn in the middle of their lines. I've NEVER seen a film where that's happened before. Their movements and the way they speak to each other is so natural.
Supreme. I loved it.