It's also a waste of time because it's a book. Deep Work, along with many other non-fiction "self help" books HN loves, could just be a couple of long blog posts. As a book it gets repetitive and tiring after the first half.
Sure, they could be, but I would argue there is benefit to expanding them into longer books.
I haven't read this specific book, but have read several other "self-help" books and while the majority of them have shown repetitive themes, that same repetition is what ingrained the overall message the author is trying to disseminate. Reading a book over the course of weeks has a much more lasting effect on me, than probably any blog posts I've read.
I read Deep Work and didn't find anything Newport says in the book to be that profound, counterintuitive, eye-opening, etc. But it's a good book and I'm glad I read it because it's, idk, 2-300 pages of ideas, however mundane, that are simultaneously good to think about and easy to accidentally ignore. As a direct result to reading Deep Work, I made a few small changes that have had a positive impact on my life since. Now, did I _learn_ anything new from Deep Work? I don't think so, but it helped me focus on things that I think I already knew.
Books aren't all about information content.