Some of them are on this page:
The first one (was on the middle of the print ad page) was from Bill Gates who said
"Ray Dalio HAS PROVIDED ME WITH INVALUABLE GUIDANCE".
Ray was someone who has agree to Bill's Billionaire Pledge idea and no doubt they rub elbows. So honestly he isn't even referring to what is in the book and why would Bill Gates even need advice from Ray? I am sure he gave him private investment ideas ... great.
Most are really lame (with no creativity or specificity) like Mark Benioff who says
"PRINCIPLES BY RAY DALIO IS A MASTERPIECE IT'S A MUST READ!"
Actually all of the quotes are all caps.
Here is what I'd like to see. Not quotes from people who have made it who have (obviously) been asked to submit a quote (they all trade quotes with each other, right). But by real people who have read a book and can document something they learned and how it helped them in their life in a specific nature.
Also I always wonder why a billionaire seems to need to write a book like this to begin with.