Asimov, of course, wrote many books about many things. In amongst the output were collections of short stories, most of which had been previously published in Ellery Queen's Mystery Magazine, of the 'Black Widowers' Dining Club'. This was a fictional dining club, but most likely loosely based on the 'Trap Door Spiders', of which Asimov was a member.
The conceit of the stories is simple and consistent. One of the members brings along a conundrum of some sort, normally embodied in a guest, and explains the situation to the others. All of the other members fail to solve the puzzle at hand, at which point the waiter Henry, who has been serving dinner and listening along, lays out the solution.
Five books of Black Widower stories were published during Asimov's lifetime, and as of recently I have them all, through from Tales to Puzzles. There is a sixth book, published posthumously, The Return, which, as far as I can tell, didn't get a UK publication. Still, I might have to get it at some point. It only contains six new Asimov stories, with others reprinted from the earlier books. One of those stories is in the Magic collection. The Best Mysteries of Isaac Asimov is split between Black Widowers (a selection from books one to four) and some of his Union Club Mysteries.