Books like Operation Time Search

Snooping around a top-secret government installation, photographer Ray Osborne stumbled across an experimental time field. Suddenly the familiar Ohio landscape disappeared and Ray found himself transported to a prehistoric world where the dread priest of Atlantis waged a war against the Sun-born of Mu. So while the scientist of the Twentieth Century worked desperately to draw him back to the present, Ray Osborne was recruited by the people of Mu to win a war that could change the course of history, and trap him in the past forever!