Writing a book does not add value to your employer, enabling engineers in the world is one thing but it does not affect your day to day job or people arround you.
yes, why would an employer want employees who have the capability to write a book on the payroll? That's time that could be spent heads-down coding! </s>
An employer would LOVE to have a 300x engineer on board.
I mean take someone like Martin Fowler who wrote a number of highly influential book and a great website. Every time you look for him, you'll find his company or employer, ThoughtWorks. He and his work have put that company on the map as one of the top consultancy firms; he and his work educate everyone that works for that company, they follow his teachings and mindset, and become "10x" because of it.
Companies would be DESPERATE to hire him. Maybe not the kind of employers you think of, no, and maybe you wouldn't hire him for his 'output', but that's a very superficial way to look at it.