This book, whilst not that information dense, contained many fascinating anecdotes about generalists who have triumphed from Roger Federer (who did not specialise in tennis all that early) to Gunpei Yokoi (of Nintendo fame). The addition of the stories kept the pages turning.
Ultimately, the book would be of greatest value to those who are dead-set on specialisation from an early age and see straying from that as a weakness. They are the least likely to pick up this book.
That said, specialisation is a valid strategy and does still work in the modern world, if you pick right.
For most who would read the book, and are already people who consider themselves generalists; it’s simply confirming their existing biases. I include myself in this group.
So, well written, but could only be categorised as “infotainment”