Cave of Wonders (Infinity Ring Series #5)

Fix the past. Save the future. Europe is in the grip of the Dark Ages, but there is a light in the dark: Baghdad. The great city has become a center of learning, populated by scholars, merchants, and explorers from all across the known world. But danger lurks in the desert . . . and Dak, Sera, and Riq must act fast to save the world's greatest library from utter destruction.