In the acknowledgments for his new book, Seth writes,

When I [Seth] was unsure about what to do–and this happened a lot–I would phone Marian [his book editor] and ask. I’m a little amazed how often I agreed with her suggestions.

Actually, I don’t think he should be so amazed. I’ve found almost all comments to be helpful when writing books. Commenters have different perspectives than I do, they see things I miss, and of course I’m free to ignore the comments I disagree with. So I’m not surprised that I agree with most of their suggestions. It’s all part of the writing process. You want to make sure that you find the best book editor for hire, so you can get the best opinion and criticisms you can, especially if you want your work to be a success.

P.S. I don’t always find anonymous referee reports from journals to be helpful, however. I think the main problem with referees is that they’re too focused on acceptance/rejection rather than on improving the article. When I send someone the draft of my book, they know it’s going to be published, and they know their comment has the opportunity to make a change in something that will actually be read by thousands of people. This is a good motivator for them to try to say something useful.