Even if I get 5% valuable feedback, it's 5% closer to being a better book, right?
In theory. . .
It might help increase your chances if you were to give readers a list of specific questions they could consider as they read. That way, they'll have a better handle on what you're looking for and can better tailor their responses. Things like, "Did you want to keep reading at the end of Chapter 1?" "Was there ever a point where something didn't make sense to you?" "Were there any times you skipped a paragraph or two to get on with the story?" "Did the conclusion feel satisfying?" Without questions like this, I think it's likely that your readers will simply read your work for the story. That is, they won't actually be thinking critically about the material, like a true editor would.
Since science-fiction is so fragmented into sub-genres, I think it might also help if you were to ask what other similar books they have read and enjoyed. If you're writing military SF, and a reader is more of a hard-science SF fan (or even a fantasy fan), then you'll have a better idea of how to interpret their feedback.
Of course, take all of this with as much salt as required! I've never written SF, although I used to be the SF columnist for PAGES magazine. (And I do know where you're coming from: I'm just finishing up my own first novel. After 25 years of earning part or all of my income as a nonfiction writer, I finally returned to my first love. Scary. But great fun.)