This is the 34th Hercule Poirot mystery, although he doesn't appear in it until about 1/2 way in.
I really enjoy Dame Agatha's books. However, this one was really rather forgettable and isn't one of her exceptional mysteries. Her best, to my mind, are Murder on the Orient Express, And Then There Were None, and Peril at End House (at least of the ones I have read). I am also rather attached to The Cat Among The Pigeons.
If you are looking for some golden age mystery entertainment to while away a couple of hours, this one is perfectly satisfactory. If you are looking for a tightly plotted mystery with a solution that isn't overly reliant on coincidence, look elsewhere.