Fire World (The Last Dragon Chronicles #6) by Chris d'Lacey-Used

After destroying a trace of dark fire, David, Zanna, and the Pennykettle dragons vanished. In a brand-new world, Co:per:nica, which runs parallel to that of Crescent Lane, firebirds roam the ancient librarium, a museum for books. But when 12-year-old David and Rosanna accidentally injure one of the firebirds, they are suddenly thrust into a remarkable adventure. The evil Ix have taken over one of the firebirds, turning it to the side of darkness, but the birds have a secret: They know about the existence of dragons. And from across the universe, one may come to their aid....