Jason Guriel on the lowly blurb. Like him, I've had reviews I've written misappropriated and manipulated by publishers to appear more praiseful than they were. Dirty pool, but you have to tip your cap, I suppose.
On the few occasions I've been asked to furnish a pre-publication blurb, I've declined, for many of the reasons Jason touches on: a)I'm not famous enough--not nearly!--to boost your sales. b)The blurb is a seriously degraded currency and I don't wish to contribute to its further decline. c)I probably won't have sufficiently unmixed feelings about the quality of your book to blurb it with wholehearted enthusiasm.
My own books of poetry have gone without blurbs, by my own wishes. The last two, we've gone with the full text of a poem, since what can tell a reader more about the contents of a book than a representative sample? I very nearly got one from Barry Lopez for my first book, but it arrived after the book had already been published. Best kind of blurb: from one of my literary heroes, but not out there for the public to see. For my book of essays, I pulled a Zizek and selected something never intended to be used for that purpose: a dismissive couple of sentences from an interview with George Bowering, who was apparently unimpressed with my reviewing work, but took too many pains to demonstrate how little he cared for it.