The 3rd novel in Terry Pratchett and Stephen Baxter’s “Long Earth” series, which Io9 calls “a brilliant science fiction collaboration.”

2040-2045: In the years after the cataclysmic Yellowstone eruption there is massive economic dislocation as populations flee Datum Globe to myriad Long Globe worlds. Sally, Joshua, and Lobsang are all involved in this perilous recovery work when, out of the blue, Sally can be contacted by her long-vanished father and inventor of the original Stepper device, Willis about The Long Mars: A Book Linsay. He tells her he’s planning a amazing voyage across the Long Mars and wants her to accompany him. But Sally quickly discovers that Willis has an ulterior motive for his request . .

On the other hand U. S. Navy Commander Maggie Kauffman offers embarked on an incredible journey of her personal, leading an expedition to the outer limits of the far Long Globe.

For Joshua, the problems he faces is a lot closer to home. He becomes embroiled in the plight of the Next: the super-bright post-humans who are starting to emerge using their “long childhood” in the community called Content Landings, located deep in the Long Earth. Ignorance and dread have triggered “regular” human society to turn against another. A dramatic showdown appears inevitable. . . .