Counterclockwise — James B. Johnson

When 57-year-old Ethan Zachary is struck by lightning, he starts growing progressively younger. Suddenly his plans to run for Congress, as well as marriage, are ruined. And although he now finds himself able to attract the young ladies, his internal clock keeps winding inexorably backwards, tick, tick, tick--until he knows that the hours are running out, any way you count them. There's just one more thing he can try! An exciting science fiction adventure.