Terry Pratchett, Stephen Baxter, The Long War

War has come to the Long Earth…

Humankind has spread across the new words opened by explorers Joshua and Lobsang a mere decade ago. Now „civilization” flourishes, and airships link the multiple Earths. A new America christening itself „Valhalla” has emerged more than a million steps from the original Datum Earth. Like the American revolutionaries of old, the Valhallans resent being controlled from afar. And in the wake of humankind's advance, the trolls - graceful, hive-mind humanoids whose song has suffused the long Earth - are beginning to fall silent… and disappear.

Joshua, now married and a father, is summoned by Lobsang. It seems he alone can confront the perfect storm of crises that could plunge all of the Long Earth into war - a war unlike any that has come before.