I enjoyed reading this book. It was a bit weird for me at the beginning but once I understood what was going on I really enjoyed it. However, it sometimes was quite difficult for me to understand that a formerly absolutely normal person as Pat would suddenly start living in a world completely of his own without much grab of reality. I know that he just blocked certain memories from his mind. But that he didn't know that he had been in "the bad place" for years seemed quite unrealistic to me.
I definitely want to watch the movie now as well. I just read the summary at wikipedia and it seems like the changed quite a bit.