We have a One-Paragraph Test for fiction. Not a complicated test, it involves reading the first paragraph and then deciding. If We are really undecided We can read a second paragraph, but that is a Bad Sign.
For non-fiction We look at the blurbs the author managed to suck out of unwilling blurbers. Well, OK, We do not really want the blurbs to be from blurbers, We want them to be reviews and We know they have cherry-picked the review sentences so everything gets discounted about an order of magnitude.
And there are two such reductions applied, the second for the source of the review. Kirkus Review of Books... well, just quoting them gets a book back onto the shelf. In the wrong section, upside-down, binder in.
Here is the Gold Standard for non-fiction back covers (hmm, the URL goes to the whole book, be clever and click "Back Cover"): The Glory of Their Times. Yes, you need to read this book, and no I do not give a rat's ass if you like baseball just read it.
We turn now to a book I have been asked to review, which will go unmentioned for the same reason I restacked it binder-in:
"This work strikes a balance between the pure functional aspects of Blub and the object-oriented and imperative features that make it so useful in practice, enable .NET integration, and make large-scale data processing possible."
The clever unwilling blurber always manages to say something nice by talking about something else, in this case the language .... instead of the book for 90% of the blurb. What does he say about the book?
It strikes a balance. Wow. How big a put-down is that? Note that the reviewer did not say "a perfect balance" or even "a good balance". And what the Hell does balance buy me anyway?
The good news is that We cannot discount that 90%, Our micrometer does not go that low. But We better check the author of the blurb.
—John Doe, PhD, Researcher, Blubber Ltd.
Oh. The people selling Blub.
The neat thing is that We now know the book is awful and that John was slowest to hide under his desk when the marketing people came around looking for a recommendation.