"The Long Earth" series of books grew to five works, with the series being ended by the death of series co-creator Terry Pratchett. The series consists of:
- The Long Earth (2012)
- The Long War (2013)
- The Long Mars (2014)
- The Long Utopia (2015)
- The Long Cosmos (2016)
The central science-fiction idea of the book is that the earth is one of a string of alternative earths, a string of worlds that are slightly different. Sometime in the near future, a man releases a simple tool, called a "stepper" that lets people travel along the earths. Although, as we find out, some people can step naturally and have been doing so for hundreds of years. The first book deals with two major topics: the social upheaval as earth as its population is dispersed, and the wide variety of life, sentient and otherwise, that occurs across the long earth.
Over the next few books, the basic premise of "stepping", while still present, becomes more of a vehicle to explore a variety of concepts. The Yellowstone Supervolcano explodes. Someone nukes Madison, Wisconsin. A race of super-advanced hominids, an evolutionary offshoot of humans, emerges. Mars is explored. Space elevator technology is developed. Cybernetic beetles destroy a planet. A nun and a monk in robot bodies become platonically married. In Victorian London, Prince Albert directs early natural steppers to help the Underground Railroad. People explore mile-high trees that use hydrogen bubbles to decrease their weight. Without giving away too many spoilers (which I have already), the books become a free range for the authors to explore biology, society and quantum physics. Although there are five books, that seems to be mostly a publishing convenience: each book has a theme, and ends with some type of cliff hanger, but in general, each book tells multiple parallel stories.
I was very familiar with Terry Prachett before beginning these books. I was not familiar with Stephen Baxter, although apparently he has a long career as a writer. From reading the book, it is not immediately obvious who contributed what. For those who mostly know Terry Pratchett from Discworld, they will notice a lack of humor and wordplay compared to those books, although the Long Earth is still written in a breezy style. The wide variety of concepts, characters and locations presented in the book might be due to having co-creators, as well as Pratchett's declining health.
One of the things about the books is how much they are "science-fiction". Apparently, Baxter is known for writing hard science-fiction. Pratchett is known for writing fantasy. While the biology and engineering in these books are scientifically interesting, the basic premise of "stepping" makes no scientific sense. People can make quantum jumps to alternative realities...and can carry things with them, through psychic force, apparently. Unless they are "phobic", then they will get very sick. Iron can't be carried over in metallic form, but iron in blood can be. The earths are separated by changes in quantum-level events, but only at a scale that makes noticeable differences from an anthropomorphic perspective. (There are, after all, trillions and trillions of quantum events happening just in my room right now: each one of these, in Long Earth terms, doesn't create its own world). The basic science-fiction idea behind the books, that people can travel through multiple-dimensions using basic technology, doesn't even try to explain its scientific basis, instead using it to explore many different topics.
These books were interesting---even fascinating, and I read all five of them in two months, due to their evolving nature and ease of reading. Despite having a central concept that might not hold much water, these books contain many fascinating stories and ideas.