While it's extra work I love those reviews.
"I haven't read this book but $THING IS WRONG, thus one " mean I can ignore some of the low ratings.
While reviews and ratings are weird and probably need some tweaking at some point[1] they are not nearly as bad as the weirdly broken search. I've got to the point where I would pay money to have better Amazon (also ebay) search*.[2]
[1]along the lines suggested in this thread - I might dislike a movie but love the genre; I might love a movie but generally dislike that genre; etc. So some method of saying why you like something so much would perhaps be handy.
[2] I go to Amazon.co.uk and I search for [microwave oven]. I chose a department - kitchen & home. I then sort by price, low to high. I am flooded with totally irrelevant items. (Egg cup; aluminum foil; salt&pepper shakers; children's cutlery sets; etc). You're not supposed to use search to find microwave ovens, you're supposed to drill down the tree of department, items, specific items.