I haven't previously encountered John's work, but was recommended this book a few times as "an essential guide to a fulfilling software development career".
The book is different from most books aimed at developers in that it doesn't cover a new language or technology, and doesn't talk about managing people or building a good development culture. Instead it tries to provide overall life and career guidance. I some parts I think it succeeds, and in others it doesn't do so well.
Big take-aways from the book are that you should treat your career like a business, even if you only ever have one customer at a time. This means effectively marketing yourself, targeting your skills at a valuable niche, and actively tracking and managing your career towards specific goals. The book includes a lot of guidance on deciding your career goals, establishing a profile and marketing yourself, how to keep abreast of new technologies and learn new skills, and how to increase productivity (for example by using the Pomodoro technique).
The first half of the book covers all this and more, and though I did feel I knew a lot of this stuff going in, I think it's covered well and there are definitely things I'll take from the book.
The second part of the book is a lot more suspect. It has advice on becoming a landlord (as if the world needs more landlords), moves into fitness (where the author's advice is fine but not what I was looking for in the book), and ends with a chapter titled "Sprit" focusing on mindfulness.
I'm pretty confident there's something in (the first half of) this book that will be new for almost every software developer working today. It's worth taking a look, but I'd probably put it down before it starts talking about the power of positive thinking.