Fiction by Agatha Christie.
I'm re-reading Agatha Christie's novels in sequential order; this was her second book. It was excellent, of course, although generally I prefer her non-Hercule-Poirot books. (He just irritates me after a while. I think this is another indication of the author's genius, though; it's like he's a real person who walks in and everyone rolls their eyes.)
It is amazing to me that this was written almost a hundred years ago and is still compelling.
I also read recently by this author: The Mysterious Affair at Styles