Over at Crime Fiction Dossier, David Montgomery ponders an important question: Can you trust book reviews?.
I certainly know what he means about having second thoughts later on, especially since the review column I write is specifically designed to recommend books. I recommended Ian McEwan's Saturday, but found I liked the book less and less the more I thought about it after the review appeared. I still think it's worth reading, because there's something interesting about it. I just don't think it's that good.
I can name, off the top of my head, one book that I reviewed this year that continues to resonate in my mind: William Nicholson's The Society of Others.
As for book blurbs, I too can think of at least one comment of mine that was not meant favorably but was edited to appear as such on the paperback edition of the book.