The author of more than 40 nonfiction books for young adults focuses on the busy period of political and commercial interchange between Asia and Europe from 1245 to 1433 A.D. Beginning with Marco Polo's famous meeting with Kublai Khan, Stefoff summarizes the growth of the Mongolian Empire and the increasing contact with Europe that began in the fourth century B.C. The oft-told but still fascinating story of the Polos is followed by a final chapter--set in the period just before the Columbus era--about two lesser-known explorers, Ibn Battuta of Morocco and Cheng Ho of China. The author's steady stream of concentrated information is well complemented by period illustrations, including a color insert, with informative captions. The sheer interest of the material here will reward those diligent enough to pursue it. Map; bibliography; chronology; index.