I have only read a review AFTER reading the book in one instance (but recently - within the past month). In this situation, it was a book which had been talked about a lot (e.g. people saying "if you like this type of genre you will like this particular book"). I didn't read any reviews before the book - had just HEARD of the book in a very positive light. To my surprise, the book wasn't really that good, and in my opinion, not on the same level as others of that genre (had some gaping plot holes, etc etc, while other parts of the plot were all too predicatable). After I finished reading the book, I thought "Gosh, I wonder why people liked it so much?" So I read a review to figure out why. I still didn't really figure it out (probably just a difference in personal tastes), but I was VERY relieved that I hadn't read the review beforehand. This is because the review gave away some of the set-up and the plot (not major parts, but still stuff I that I believe was best discovered by the reader during the book, not by the review).