If you live in a building older than a few decades, you’ve probably daydreamed about what the world was like when it was built—or who designed it. Every once and a while, the “who” turns out to be pretty interesting.
Sir Terry Pratchett first came up with the idea of the Long Earth multiverse back in 1986. He set it aside to focus on Discworld. The 75 million copies sold of those wildly popular fantasy novels would indicate that this was a pretty good idea. Even the Queen of England agrees.