Take a look at the book The Hacker Hunter
Currently the book has six reviews and they are all one or two stars. In several of the reviews there are mentions of over two hundred "five star reviews" for the book. It looks like Amazon removed all the five star reviews because it looks like they were placed by the author.
Here is one of the reviews: This is the first time I've reviewed a book, though I read a lot. Now that I'm in the Kindle world, I usually read a book a week or so. I've experimented with some of the highly rated Kindle offerings and I've been pleasantly surprised - this seems to be a revolutionary way for new authors to get their books and their names out there. But there is always the drawback - fake reviews. I bought this book because it was loaded with raving reviews. After struggling through half of the book I finally had to stop - it just wasn't read-able! Those reviews were obviously faked. I've noticed that the number of reviews has been re-set or something, so Amazon obviously caught on to the problem. Anyway, don't buy this book - it truly is poorly written.