On a couple of the book pages on Facebook, I've had authors approach me for a 'review for a review'... they were all from non-English speaking countries and a quick look at their books was mind blowing. They had quite a few five star reviews but the books were unreadable tripe - rubbish cover and blurb, bad formatting, total garbage writing with sentences that didn't even make sense. They were so addicted to the notion of greed and making money at any cost, that they saw nothing wrong with cheating to get good reviews for rubbish, with the expectation that good reviews equalled sales. It was sad - the art and craft of writing reduced to a sick by-product of greed.
I was polite. I reported the books... nothing was done. They're still on Amazon for sale. I wish all those rubbish books that clearly have fake reviews and which are garbled rubbish were removed from Amazon. That extends to the products that have spawned this industry of paying for reviews.