Principles was a great book for me because it comes from someone who is very successful according to our society's criteria. Ray Dalio has built the biggest hedge fund in the world.
Many of the books you can read relating to personal growth can sometimes seem a bit far fetched. I read recently the Law of Attraction and Joe Dispensa's Breaking the habit of being yourself, and the concept can be hard to grasp when you are for example in a corporate environment.
This is why I like recommending Ray Dalio's book, I know people will have a good first impression considering the author. And Ray Dalio raves about meditation, which resonates better with some people than similar advice given by a monk.
When it comes to the content of the book, I would say that I loved the life's principle, however I found the first part, more personal, and the third part, on work's principles, a bit boring. Maybe it's because I've now read quite a few books on the subject.
Within the life's principle, I loved a few concepts, like radical open-mindedness and tough love. I love the combination of being very honest and transparent but doing so from a place of love. He also explains very well how you can work efficiently as a team, which in the end is the most important if you want to achieve great things... you can't do it alone.
This book has pushed me to be more clear on my mission, vision and values and to work more with other people which is an important step. So I definitely recommend it, but I really find it too long. It has also helped me define how much we can bend reality versus accepting reality before changing it, and balanced out the Law of Attraction for example.
Have a look at this animated video which is a great summary and a must-watch. Then you can judge for yourself if you want to go ahead and read the book.