Thebes of the Hundred Gates — Robert Silverberg

Edward Davis, a rookie of the Time Service, has already made several successful jumps to the past. Now he is given his most important mission.Two members of the Service have disappeared in ancient Egypt and Edward Davis's assignment is to locate and rescue them.But is he ready for all that Egypt has to offer and for the surprising truths he discovers as he explores this ancient land of myths and mysteries -- truths that jeopardize his own mission and return back to the future?