What Are the Best Sci-Fi Books or Series Employing Parallel Universes?

“If a coin comes down heads, that means that the possibility of its coming down tails has collapsed. Until that moment the two possibilities were equal. But on another world, it does come down tails. And when that happens, the two worlds split apart.” —Philip Pullman, The Golden Compass

We've probably all seen the question floating around, the one asking what you'd be doing right now if there weren't a worldwide pandemic dramatically altering your life; the question, what is going on in your own personal parallel universe? For most of us, it's not terribly hard to imagine because, well, it'd just be our lives, as usual. The question isn't asking us to draw on our imagination, rather it's a hat-tip to acknowledging that this shared experience is hard. That, quite likely, we are all giving up, or missing out on something. That said, we can't be the only sci-fi lovers who hear the question and find our mind wandering toward the parallel universes of science fiction. And Those? Those are another thing altogether. 

Our favorite science fiction writers have been imagining parallel universes for about as long as science fiction writers have been writing. While it can be a tricky tool to pull off well, some of the stories that have come from these imaginings are among the very best sci-fi has to offer. This week, we're asking you to think about your favorite books employing parallel universes and submit the ones you think are the very best.

We've jump-started the conversation with a few suggestions of our own, but in order for these polls to be truly representative of the favorites of our community we need your submissions! As this is the first round of voting, please feel free to add as many nomination(s) as you'd like and then be sure to vote for as many as you'd like as well. 

As always, we base our lists on the votes and nominations from this blog and our Facebook Reader group, and we want to hear your opinion!