There is an interesting article where some very famous bestselling authors are condemning fake book reviews, including Lee Child and Susan Hill.
In this article it states:
The practice, known as "sock puppeting", has been given added salience by the recent disclosure that best-selling crime author, R J Ellory, whose novels have sold more than a million copies, has been using fake identities to write positive reviews of his own books, his "magnificent genius" and critical attacks on his rivals.
It also says this:
The practice of sock puppetry is not merely dishonest, it is in England and Wales illegal under the 2008 Consumer Protection from Unfair Trading Regulations, which makes it a crime to pretend to be a consumer and leave positive reviews of one's own products.
I recommend reading the article in full, here.
There are links within this article that will lead you to other articles that are just as interesting.