Maupassant wrote over 300 stories in a very fertile 10 years, in addition to 6 novels and travel writing, but as there aren't any modern complete editions in English, today's monoglot reader has to buy as many selected works as possible to get the full range of his oeuvre. I have 9 collections, containing over 120 different stories.
This one, a recent Penguin Classics edition, very consciously focuses on some of the lesser-known stories, although it does also have some classics such as Boule de Suif and Le Horla. Boule de Suif was the first Maupassant story I read, which is usual as it's his most famous, and often the first in a collection as it was the first he published. Rereading it, now with some understanding of Maupassant's themes and techniques, I found it extraordinarily accomplished. It could be said that he didn't surpass this in 300 subsequent stories, although he experimented with different forms of the story.
Not all the stories in this collection are excellent. Some are quite average, and many very slight. Moonlight, for example, is an ironic tale about a devout parish priest, who is scandalised to hear that his niece has a lover. Walking under a moonlit sky and considering the matter, he undergoes a 'conversion' stimulated by the conclusion that God must have designed such charm for the purpose of desire. It's a witty inversion of a moral instruction, and very short, but a little too neat.
Femme Fatale (or La Femme de Paul) on the other hand is rather more overt - a man loses the girl he's obsessed with to a lesbian. Maupassant doesn't bother with euphemisms, it's quite plain what he's discussing, and it's for stories such as this that he became notorious in Victorian England. He gained a reputation for being very risqué, although few of his stories are as challenging in their treatment of sex, as this one is. But it's all relative - Maupassant's open discussion of desires and affairs was far from what publishers in England would allow.
The best of this collection are the well-known ones - in addition to those mentioned above there are The Jewels and The Necklace, which are sort of counterpoints, both hinging on the veracity of some jewelry, and concerned with how fundamental deception is to society. Regret is one of his archetypical stories, Maupassant's imitation of an impressionist painting, perfectly capturing one emotion in a single scene.