I ask this because I know my personal taste in most things is vastly different from other people. I assume this holds true for everyone. So why would you let someone else who likes different things than you tell you how good a book is?
I get movie reviews. The story is laid out for you. You don’t have the liberty of imagining what the characters look like, how they speak. It’s also much more limited than a book in that it needs to fit neatly into about an hour and a half. Now, I can guzzle a book in a day or less but I don’t think I’ve ever finished anything with a proper storyline in that amount of time…maybe a Sweet Valley High or something, but definitely not a normal-sized adult (and I don’t mean “adult” in a 50 Shades of Grey sort of way!) book. So if there’s bad acting, if the climax sucks, it’s probably a fair assessment that a movie review would be useful to most people.
How many bad books have you read, but you finished anyway because you felt you needed to see how the story ended? And how many movies have you stopped midway through because they were horrid? Maybe it’s just me, but I’ll finish even the most horribly written books just because I felt compelled to, but I could care less about a bad movie.
In conclusion: I’ve never bothered with a book review, but judging by the internet, there certainly seems to be a plethora of them. So who’s reading them?