I don’t think this is one of Asimov’s best stories – and I’ve read many, as he happens to be one of my favourite authors. However, it does a good job of illustrating some of the…pitfalls…of playing the “What if?” game using the costruct of alternate reality.
In this short story, a woman is travelling with her husband on a train. She’s somewhat insecure about herself, so is constantly playing the “What if?” game. Which she proceeds to do while sitting on the train. In a somewhat surreal turn for Asimov, along comes a character who offers her a chance to see what her life would have been like if….
The story is well written, and keeps to the point. Somewhat amusing. Not much else, really.