Competitors could buy and read the book, but it wouldn’t help much. As the earlier poster said, Trump has been doing this for years. Even with knowledge in their heads, competitors would have to get up to speed and it would take time. With Trump, I think a great deal (no pun) of it is instinct.
In the technology journal I publish, I often interview consultants who are paid a high price for their advice — and they give away lots of valuable advice in the interview.
Now maybe a few enterprising people will follow that advice directly. But a surprising number people — if they have a need for that expertise — will actually hire the consultant because of the extra value of instinct.
So yes, it all does boil down to instinct. The expert is valuable because his many experiences have allowed him to gained instinct. . . or wisdom perhaps.
But curiously, Shakespeare could never explain how Shakespeare writes his magic.