Time Trap - Deborah Chester

When a time-traveler is mistakenly sent to Medieval Greece, he finds bandits, Crusaders—and his own evil twin—in this sci-fi series debut.
In the 26th century, chaos threatens to overwhelm civilization—but the historians on staff at the Time Institute are determined to change things for the better. By gathering first-hand recordings of history's greatest events, they hope to restore faith in humanity and inspire the modern-day populace to pursue its own achievements. But when anarchist saboteurs infiltrate the Institute, time-traveler Noel Kedran is sent to the wrong place and century.

Medieval Greece is little more than a way-station for European knights headed for the Crusades. This small pocket of history is awash in treachery as Greek bandits, French knights, and Constantinople's diplomats battle for supremacy. Caught in their clash to rule Greece, Noel fears that any alteration to the course of history could destroy his own time. But then he meets his own mirror image—a doppelganger as determined to destroy the future as Noel is to save it. And he's ready to take both history and Noel's fate into his own hands.unless Noel beats him to it.