The Gate of Worlds — Robert Silverberg

An Alternate History adventure...From Turkish dominated Europe, across the high seas to the land of opportunity--the Aztec Empire-- Dan Beauchamp is a young Englishman whose heart longs for fortune and adventure. But industrial Mexico is a long way from primitive Britain, and Dan has a lot to learn.From the city of London--better known as New Istanbul--to the untamed wilderness of North America lies a high adventure not to be missed.