Did you watch the
Writing Killer Blurbs seminar?
If you did, watch how critical he was of his own early blurbs, and what he saw in other blurbs that he rated highly. But, in order to write a full blurb for a submission, he'd have to know a lot more of the story than the opening 700 words, and a good synopsis of the story, too.
Guests may be in the same boat as a reader and not know the deeper purpose of the blurb as a sales-oriented weapon so it's appealing to their sense of intrigue, rather than rating it based on the 'shape' of it to suit a purpose.
Using copywriting strategies, the shape of the blurb has an inciting opening or header section (the attention-getting), followed by teasing fill in the middle (the emotional entanglement), and ending with a form of something that calls the reader to take an action (CTA).
Finding ways to put that around a book-blurb is still a nightmare, but knowing the shape for a blurb is like knowing the structure for a story - it's the start of the blurb story, not a strait-jacket.
Well, that's what I think and feel about it, and although this knowledge has improved my blurbs, I think I still have a long way to go to get a deeper understanding to enable a highly-rated response from Pop-Ups!