Whilst I was in the middle of lamenting yesterday how difficult it is to write fantastic phrases about new titles that would have booksellers tripping over themselves to order copies, (if only...) Vic Peterson in Contemporary Poetry Review must have been thinking along similar lines in respect of jacket copy, see: Spillage from the Riptides of Desire: Poetry Blurbs cprw.com

I've lifted a small quote from his article below. "... a book’s jacket copy blurbs are recommendations—a way to convey the product’s style and promise. A blurb, in this respect, is a kind of mini-book review, and the eminence of the recommending writer lends credence to the praise. A few words of approval are by no means as thoroughgoing as an essay in a literary periodical; but the point is not entirely different, at least if the writer’s loyalty is to the reader. Honest book reviews toe an ethical line, and jacket commendations aspire to a similar integrity of judgment; a good plug turns you on to the right book for the right reasons..."

I suggest you read the whole article - it's very good. All I can say is, thank goodness I don't have to write jacket copy.