I had a lot of fun reading this. It is very short, just over 200 pages and I would recommend trying to read in one or two sittings. The one thing that I did find was that it had a very exciting beginning, had a brief lull (possibly caused by where I decided to break off reading) and then got exciting at the end again.
So it starts off with a man who claims to collect murders. Yes I bet you are looking as baffled as I was when I first heard/read it. But it's true he claims to work out people's secrets and enjoys spending time in their company. Problem is he gets murdered while sitting in a room with four people playing bridge - one of whom is the murderer and the other three saw nothing.
Could be an impossible crime for Poirot to solve. All I'm saying is that it was brilliant. Health warning - don't read it before bed, work or any important important. You will neither sleep or be on time. I nearly didn't get off the train at the right time, because, well, there is always time for one more page!