Be My Enemy — Ian McDonald

Everett Singh has escaped with the Infundibulum from the clutches of Charlotte Villiers and the Order, but at a terrible price. His father is missing, banished to one of the billions of parallel universes of the Panoply of All Worlds, and Everett and the crew of the airship Everness have taken a wild Heisenberg jump to a random parallel plane. Everett is smart and resourceful, and from the refuge of a desolate frozen Earth far beyond the Plenitude, where he and his friends have gone into hiding, he makes plans to rescue his family. But the villainous Charlotte Villiers is one step ahead of him. The action traverses three different parallel Earths: one is a frozen wasteland; one is just like ours, except that the alien Thryn Sentiency has occupied the Moon since 1964, sharing its technology with humankind; and one is the embargoed home of dead London, where the remnants of humanity battle a terrifying nanotechnology run wild. Across these parallel planes of existence, Everett faces terrible choices of morality and power. But he has the love and support of Sen, Captain Anastasia Sixsmyth, and the rest of the crew of Everness as he learns that the deadliest enemy isn't the Order or the world-devouring nanotech Nahn -- it's himself.