I agree that you get most of it by reading HN for a few years. However, it is a small old book so not that much of an investment.

It did have a few ideas which were new to me and it presents a holistic consistent management philosophy which you don't get from reading a hodge-podge of blog posts.

Two (for me) new ideas: Matrix organisation is inevitable for large companies in search of the sweet spot between agility and efficiency. Knowledge workers are middle managers.

Overall: Good book but not "you have to read it" level.