Maybe the stories, taken as a whole, don't deserve 5 stars, but the very idea of assembling 100 SF tales, mostly of 1,000 words or less, is a stroke of genius – so not surprisingly, they were assembled by SF's one registered genius, Isaac Asimov. And not surprisingly again, his own opening story, "The Last Answer," is probably the best in the collection.
Where could all these tiny attempts have come from? Quite a few are "original to this collection" ("Hey, Jose, it's Isaac, I'm doing this thing, want to whip up a quick 1k tale?"). For the most part, these are not the best ones, more often uninspired dribbles with a trick ending (though with "Dreamworld," Asimov – again – pulls off a short goof designed simply to end with one of the most hilarious bad puns in all of literature). Several of the "originals" carry obvious pseudonyms – who, I wonder, was "R.K. Lion" (P.K. Dick maybe?)?
A few are serious, thoughtful attempts at examining the human condition or riotously funny asides, and they're mostly by women: "Friends," by Roberta Ghiadalia, about a girl and her cat, is dark and disturbing; Joanna Russ's "Useful Phrases for the Tourist" should not be read on the toilet because you’re likely to fall off the seat laughing; "And So On, And So On," by James Tiptree, Jr., is textured, downbeat and unnerving (it wasn't generally known at the time that Tiptree was a woman).
A fine collection to have at hand for a quick read while the tea water is boiling.