The Long Mars (The Long Earth #3)

Terry Pratchett; Stephen Baxter

2040. The Long Earth is in chaos. . . . The cataclysmic Yellowstone eruption is shutting down civilization. Whole populations flee to the relative safety of myriad stepwise Earths. Sally Linsay, Joshua Valiente, and Lobsang have all been involved in the perilous post-eruption clean-up. But Joshua face...