This is a collection of 16 original science fiction short stories, plus one novella, written by 17 authors and assembled 32 years ago in honor of Isaac Asimov shortly before his untimely death. Inevitably the quality is uneven, but the good ones definitely outweigh the bad. So pick up a copy from your library and give it a shot!
The title, of course, hints at the idea that the stories take place in the universe of the Foundation series, and indeed most of them do. But by no means all. Some are in the robots series, which got eventually merged with Foundation, as I’m sure you know. The best story, set squarely within the Foundation universe, is a serious novella by Orson Scott Card. There are also humorous stories by Connie Willis and Robert Sheckley, alternative-history stories by Frederick Pohl and Mike Resnick, and other instances of sf sub-genres.
You won’t like everything. You probably won’t like the same stories that I liked, and vice versa. But you’ll enjoy the collection as a whole. And don’t omit the two prefaces, one by Ben Bova and one by the usually insufferable Ray Bradbury, or the two afterwords, one by Janet Jeppson Asimov and one by the master himself.