The book is relevant to the topic being discussed, because the author talks about it to describe how she herself -- purportedly a successful published author -- has to fight off feeling inadequate, even though she's being paid by her publisher to travel cross-country to promote her book.

Take out the mention that she's on book tour, and you no longer have a frame of reference about her self-shame.

> It's more like "Hey! I wrote a book on this exact issue. I really hope it helps"

Except that's your notion and not what Polly was doing with their book mention in the article. There it served as a way to kinda say, "Hey, I also share some insecurity issues with you, caused this by book I'm touring on right now, and oh, here's the link to it". There was no other nudging of Haunted to read the book.

First part was probably embellished anyways. Anyone can make up a two part sob story style q&a for promotional purposes.