Rewrite — Gregory Benford

In this thematic sequel to Gregory Benford's award-winning bestseller TIMESCAPE, a history professor finds that he is able travel back to 1968, the year he was sixteen -- here, he finds a slew of mentors with the same ability, including Robert Heinlein, Albert Einstein, and Philip K. Dick and becomes a successful Hollywood screenwriter until some wicked time travelers try to subvert him.