I was talking about sales hook, which is what an editor tries to think about when acquiring. You're right, the hook you use in your query letter can't be "great writing" because dammit, the editor will be the judge of that. The sales hooks that depend on someone's judgement don't work until you have the judgement of someone the reader/editor trusts. This is the thing that makes me hate pitch sessions—there's no way to judge the writing, and the writing's the main thing. But any non-judgement-based sales hook works in a query letter.
When talking about hooks aren't we talking about the one or two sentence "thing" that will get an agent, editor or reader to read the ms or book?
When you talk about a book being wonderful, or written well, or having a great story, you aren't talking about the hook, are you? Because those are the things you know about the book after you've read it, whereas the hook is the thing that gets you to read it.
I'm wondering what would be the thing in a cover letter for Speak, or Hattie Big Sky, (before they became what they became) or any other title that would prompt you to read the first three chapters? Isn't that what we're talking about when we talk about hooks -- how to pitch one's work so that the hopefully great writing will get read?
In the case of a query letter for a book that has no particular hook aside from great writing, two to three sentences of plot description is what you have to work with. But after reading thousands of pieces of slush and who knows how many pitches, editors get really good at telling good writing from bad over the course of a letter. Really.
You're only going to sabotage yourself at this if
a) you overthink it and get all nervous.
b) you don't know what your manuscript is really about.
c) you can't write.
Let's assume it's not (c), and you get a grip on yourself and avoid (a). I see a fair number of people who seem to have a pretty good idea of what their manuscript is about, and are certainly willing to give it their best guess. This is not good enough. You figure: of course I know what it's about; I wrote the thing, right? Wrong.
It's good for you to practice looking at your stuff the way a stranger would. You love all of it, but what's the coolest part? What's the shiniest, prettiest, wiggliest, most shimmering part? ;)
Take Speak and Hattie Big Sky as encouragement—clearly it is possible to get a manuscript read and published without the kind of hook you'd put in a query. But if there is one, use it!