It's a book and a film which repackages some of the ideas of positive thinking and new agey ideas. It has been featured on Oprah etc. but has also come in for a lot of criticism because of its core idea that you can will anything into existence by thinking it will happen, so for instance, it suggests that by taping a cheque to your ceiling, you will start to receive lots of money without explanation. The writers have been taken to task for suggesting that people who died in the tsunami or 9/11 etc. must have been thinking negatively to be in that place at that time. So, as you can see, it's not without controversy and many people believe it has a brainwashing element to it.If you google criticisms of it you'll find plenty written about it.
Having said that, there are ideas in there like the law of attraction which have been written about in other books with less baggage attached. If you do an amazon search you can find stuff on positive thinking, but also more 'scientific' types that involve elements of cognitive behavioural thinking. There's definitely something to be said for thinking positively as much as you can, but we're all human at the end of the day and people shouldn't be held responsible for having human emotions, so personally I steer in that direction. Just my opionion though. HTH xx