The content seems useful and is corroborated by both what I already knew and have heard from reputable sources, e.g., regarding polarized training, which is what the book endorses. I think the book is worth reading if you are interested in and especially self-coaching in the relevant sports.
The book, however, would have been improved with better editing:
As others have noted, obvious errors remain throughout the book, these are often only typos or photo captions that have been duplicated across multiple photos, but in some places the authors seem to say the opposite of what they are intending, e.g., on page 119: "Typically this type of fatigue is self-limiting as your ability to contract those muscles powerfully will naturally end that type of movement; you can manage one more pull-up." I assume they meant that it is self-limiting because you eventually can't manage one more pull-up.
30-40% of the book is comprised of beautiful photos of people outdoors. Another 10% is "Athlete stories". These are often inspiring, but make the book twice as long as it needs to be. They also often interrupt the main text in a way that makes it difficult to pick up again. It also makes it harder to use this book as a reference.
There is quite a bit of repetition of both the main ideas and specific features of types training weeks (which are sometimes copied nearly verbatim several times).