This is curious, because my g/f (who read the book and liked it) posted a good review of a novel I wrote and her review was removed because Amazon figured out she knew me. I have no idea how they did this: we don't live together and I'm not sure I've ever bought her anything off Amazon, certainly not at her present address.

So I have the impression that Amazon is pretty good at weeding out good reviews from people you know, while still being complete rubbish at policing obvious spam reviews, and doing a terrible job of suppressing reviews from obvious trolls (my book has a two-star review from a guy who also gave "A Tale of Two Cities" a two star review, but you wouldn't know that unless you looked at their review history, and who can be bothered to do that?

As both an author and book-buyer, Amazon's review system is a complete loss. Every single book I look at has both good and bad reviews with almost no way to tell if they are based on standards at all relevant to my taste. Any review that doesn't say something along the lines of "My taste runs to X and this was a great example of X" or "My taste runs to Y and while this was kinda-Y-like it failed in these respects" may as well not exist.