Book excerpt: The Long War by legendary author and Discworld creator Terry Pratchett and award-winning science fiction novelist Stephen Baxter follows the adventures and travails of heroes Joshua Valiente and Lobsang in an exciting continuation of the extraordinary journey begun in the New York Times bestseller The Long Earth. War has come to the Long Earth.... Humankind has spread across the new worlds opened up by stepping, which Joshua and Lobsang explored a mere decade ago. Now "civilization" flourishes, and fleets of airships link the multiple Earths through exploration, trade, and culture. Humankind is shaping the Long Earth, but in turn the Long Earth is shaping humankind. A new America that has christened itself "Valhalla" has emerged more than a million steps from the original Datum Earth. And like the American revolutionaries of old, the Valhallans resent being controlled from afar by the Datum government. In the intervening years, the song of the trolls—graceful, hive-mind humanoids—has suffused the Long Earth. But in the face of humankind's inexorable advance, they are beginning to fall silent . . . and gradually disappear. Joshua, now married and a father, is summoned by Lobsang. It seems that he alone can confront the perfect storm of crises that threatens to plunge all of the Long Earth into war. A war unlike any that has been waged before... The full list of books in the Long Earth series include: The Long Earth The Long War The Long Mars The Long Utopia The Long Cosmos