Presumably the five star rating is in part due to the amount of work it took to complete the book - in the sense that I probably felt a need to justify having read this book due to the amount of time it took, and if I could convince myself that the book was good this would be an easier thing to do. On the other hand I did make a decision reasonably early on that if I did decide to eventually rate this book, I'd most likely have to give it five stars; the only plausible alternative to giving the book five stars was not rating the book at all - I could never have justified giving this book a low rating even if I'd found myself unable to finish chapter 7, as this would have implied implicitly punishing the authors for basically providing quite exhaustive coverage of the topic(s) at hand.
Some of the content, especially in the later chapters of the book, is quite difficult, especially if you're not willing to spend quite a bit of time on it, but many key ideas are developed and explained in a manner that makes them relatively easy to understand if you have the proper background. A lot of the stuff in this book is stuff it would be easy to argue that people working in the applied sciences ought to know, and it would also not be hard to argue that some of these things (especially the ideas developed in the first few chapters) should likewise be known by non-scientists who would like to hold opinions about science and scientific research.
The book was written some years ago, so some progress has presumably been made in the meantime especially when it comes to concrete applications (due to computing power developments since the book was written - this is probably especially relevant in the context of the application of numerical methods and how to apply the bootstrap) in specific contexts which were not well-explored at the time of the publication of the book. However most of the main points of the book are based on deep theory from information theory and mathematical statistics, so the publication date should not in my mind be considered a strong argument against exploring the ideas presented in this book.