2070-71. Nearly six decades after Step Day and in the Long Earth, the new Next post-human society continues to evolve.
For Joshua Valienté, now in his late sixties, it is time to take one last solo journey into the High Meggers: an adventure that turns into a disaster. Alone and facing death, his only hope of salvation lies with a group of trolls. But as Joshua confronts his mortality, the Long Earth receives a signal from the stars. A signal that is picked up by radio astronomers but also in more abstract ways – by the trolls and by the Great Traversers. Its message is simple but its implications are enormous:
The super-smart Next realise that the Message contains instructions on how to develop an immense artificial intelligence but to build it they have to seek help from throughout the industrious worlds of mankind. Bit by bit, byte by byte, they assemble a computer the size of a continent – a device that will alter the Long Earth’s place within the cosmos and reveal the ultimate, life-affirming goal of those who sent the Message. Its impact will be felt by and resonate with all – mankind and other species, young and old, communities and individuals – who inhabit the Long Earths…
In this conclusion to the Long Earth series (following 2015's The Long Utopia), set in 2070, Baxter (Ultima) and the late Pratchett (The Shepherd's Crown) take their decades-spanning tale of an infinite chain of parallel Earths to the next level as a mysterious signal from the far reaches of the galaxy urges humans to "join us." While the ultra-intelligent subset of humans known as the Next build a continent-sized supercomputer on a distant Earth to further decipher the message, the famous explorer Joshua Valiente takes a sabbatical far from home, which leads him to an eye-opening encounter with nomadic trolls. Eventually Joshua joins the crew of humankind's inaugural interstellar mission and discovers just what lies at the heart of the galaxy. The story starts off slowly, but it quickly picks up speed as the mystery deepens and the myriad threads come together. There's a definite sense of mortality, but also a sense of wonder as the characters embrace the vast unknown in what might be considered the perfect allegory for Pratchett's final years. It's a wholly satisfying conclusion to the series, though vast amounts of potential remain in the concept.