The Lathe of Heaven

George Orr (try to say that without thinking of George Orwell) is having dreams. Trouble is, they are coming true and retro-actively changing reality and history. Only George remembers the previous history and knows that it has been radically changed. He tries to drug himself into dreamlessness but ends up in drug therapy with a psychiatrist dream researcher who sees an opportunity to gain power. But as the power hungry psychiatrist hypnotises George into dreaming certain events, the dreams are not so controllable and become increasingly dangerous in a 'be careful what you wish for' kind of way.

The book is a rush of alternate histories that leave George scrambling to remember what is the current reality and what has changed. It's like 'The First Fifteen Lives of Harry August' except that Harry has some control over his various histories. And in each book they meet the woman to whom they were married in a different stream/life and have to decide how to relate to her.