This is the first book in a series called the Merchant Princes. I'd say it was frothy entertainment, done pretty well. A few people have the genetic ability to move back and forth between the present day and an alternate universe set on what appears to be the same planet, but to what looks like a period about 200 years earlier, and where history is a bit different. They use this remarkable ability to run a business that exploits the differences. A woman with this ability is orphaned as an infant, raised as a middle class American, and discovers her ability when she's 32. Consternation ensues.