I've got to admit, when a book has nothing but blurbs and praises for the author, it goes back to the shelf unless it's a book by an author I'm already a fan of. Harry Dresden, Repairman Jack, Miles Vorkosigan, Bob The Nailer? I'm on those like ugly on an ape even if the book has nothing but soup label ingredients printed on the cover. Barring those happy few, I want to know at least roughly what the basic premise of a story is before I hand over my hard earned happy joe money bucks. Too many authors mumble vague praises of other books their publishers are pushing for me to feel a lot of trust. Now if an author I'm familiar with talks up another author or book on their blog or website, then I'm more willing to place more weight on it. "A fast paced roller coaster" type statements carry no weight for me, but give me a couple paragraphs where an author I respect actually discusses the book, then I'll give it a whirl.
What I really hate is when the plot synopsis is an utter misrepresentation of the book. Don't tell me the book is about an ancient horror that's awakened and is stalking the dark alleys when the book is actually focused on a girl was sad and drank a glass of water.
Unless of course it's ancient evil horrible water that will make her stalk the dark alleyways bringing blood and terror.