The Regatta Mystery is a collection of short stories that feature Hercule Poirot, Parker Pyne, Miss Marple. From jewel thefts to murders of men stuffed in trunks, this collection had a good variety of mysteries. There are several that aren't mysteries at all, but supernatural pieces by Dame Christie.
I didn't really like this one, but maybe that's because I'm not as fond of her short stories than I am of her actual full length novels. You get less time to try to figure out the mystery on your own, and she usually throws a curveball right at the very end, which ruins everything. You have to base your assumptions more on feelings and knowledge of previous similar cases to guess right.