As a prospective purchaser of a book, how can you differentiate between these two types of reviews? It's actually relatively easy in my mind. When you are on your favourite bookstore website, you will see the reviews towards the bottom of the page. With the review, you'll most likely see the name of the reviewer and it is underlined as a hyperlink. Simply click on the hyperlink and you will see ALL of the reviews that this individual has left. From there, it's usually pretty much a no-brainer to figure out if they are a legitimate reviewer or not. I've clicked on the books of a few 'suspect' authors and when I clicked on the links of their 'reviewers', I could see that the same individual had also reviewed 6 other books that day, all with glowing 5 star ratings and gushing reviews. This was a dead give away to me.
How do you know which authors' books to investigate? Well, this is another of my theories on the realities of ratings. As far as I'm concerned, if an author is claiming that they have > 50 ratings and that > 95% of them are 5 star, this would make me question the legitimacy. I don't care how great a book is, there will always be those that like it, those that love it and those that just hate it and the distribution of star ratings should reflect something along those lines. I can certainly say in my own case that my opening chapters of "Pieces of Silver" on the Kobo bookstore reflects this. 7 out of the 10 ratings are 4 or 5 stars, but I also have one 1, 2 and 3 star rating. This is the reality, there'll always be someone out there who doesn't like one of my stories and that's completely okay. As an author, I've got to write for those who enjoy my stories because I will NEVER be able to please everyone, nor will I ever be able to claim that 95 out of my 100 ratings are 5 star reviews!