I don't usually let reviews influence me too much before I decide to read a book, although a book that I'm iffy about with an unusually low average rating will give me pause. But after I read it, I look up the reviews, and if I find myself nodding in agreement and saying, "Good point, I didn't notice that," what other people have written about the book will sometimes influence how I feel about it.
This usually happens when my initial estimation of a book is somewhere between N and N+1 stars, and observations by other reviewers will weight my final rating up or down. I've never changed my mind so radically after reading others' opinions that I changed a book's rating by more than one star.
Here are some observations after having looked at a lot of reviews.
By the numbers
Both the average rating and the mode (the rating most often given) are fairly indicative. Note that all of this analysis assumes a book with a significant number of reviews. If only 10 people have rated it, then the averages aren't too meaningful, though the written reviews may be, depending on their quality.
Most books have an average rating between 3.4 and 4.4 stars. Anything lower than that is probably a pretty mediocre book. Especially if the mode is 3 stars or less.
Really good or really popular books almost always have a mode of 5 stars. The difference between "good" and "popular" is that good books have a small number of low ratings.
While even the worst books will have a few 5 star reviews, and even the most beloved will have inspired enough hatred in a few people to give it 1 star, any book whose 1 star reviews make up more than 1% or 2% of the total has done something to piss off a lot of readers.
Either that, or it was mandatory reading in English class, and thousands of high school students have descended upon its review page to express their resentment.
Then there are books that probably weren't actually read by the majority of people rating it.
Snarky is funny, but eviscerating is better
I love a bit of snark, though I prefer it when it's thoughtful snark. But I love reading long, well-written one star reviews, even of books that I gave five stars. Because while I might disagree with the reviewer's overall estimation of the book, I almost always find that their criticisms are (mostly) on-point. Sometimes it's stuff that I noticed but which just didn't bother me, or not enough to diminish my enjoyment of the book. Other times they actually point out things I didn't notice (and as mentioned above, sometimes that makes me reevaluate the book myself). It's really quite worthwhile to read reviews that take a book apart from a different perspective.
For some reason, I don't enjoy glowing reviews of books I hated as much. It's not because I disagree with the praise, but I've found a person's reasons for loving a book are usually more personal, while their reasons for hating it are usually because of specific things that set their teeth on edge. People love a book because they got lost in it, because it made them feel good, because they cared about the characters, and that may or may not be something that someone else feels. People hate a book because it broke their suspension of disbelief, because they hated the characters, because they thought the writing was crappy, because they picked up on a theme that they loathed. You may or may not disagree with things like that, but you can pick them out and identify with them and evaluate whether and why you disagree.
Was This Review Helpful? NO!!!!UR SO MEAN!!!!
So we all know there's a certain segment of fandom that will scream bitter tears of butthurt if you criticize what they love.
This has led me to pay attention to reviews of reviews, i.e., the Amazon "Was this review helpful to you?" buttons. Bad reviews, no matter how well-written, usually get a lot more "No" votes. I've written mildly critical reviews that were long, thoughtful, and not even particularly snarky and been surprised when suddenly 0 out of 3 reviewers thought they were helpful.
I find this amusing and frustrating -- read through a lot of review ratings and it's evident that many people vote on a review not based on whether it's a good review, but whether they agree with it.
Of course a review that is nothing but "OMG I loved this!" or "This book sucked and was a waste of my time" (the latter of which, honestly, comprise the majority of one-star reviews) isn't helpful or interesting. But I appreciate people who take the time to write a long and detailed review, even if it's savage.
What's worse than poorly-thought reviews, though, is reviews that aren't actually based on the quality of the book. For example, Stephen King's new book, Full Dark, No Stars, has been getting panned on Amazon, not by people who didn't like it, but by people who are pissed off that the Kindle version is more expensive than the hardcover.
Making authors cry
What's even funnier than butthurt fans crying that someone panned their favorite author? When the author does it.
I can understand authors being upset when their book is getting one-starred because of the price (something over which they usually have no control). But I must confess that one of my favorite kinds of wank is author wank. Nothing is funnier than an author getting into fights with reviewers. Or writing brilliant reviews of his own books under a pseudonym.
First rule every author should internalize is "Do not respond to reviews," but some just can't help it.
Occasionally, they do so with grace and humor. (And btw, OH JOHN RINGO NO is one of the best head-splody reviews ever written... go read it.)
More often, they make an ass of themselves.
I confess that when I find out an author has responded to negative reviews with whininess (I'm thinking Jim Butcher here, but I can't find the link to one of his LJ posts where I saw him post a bunch of negative reviews and cry that it was unfair that people were saying such mean things about his books), I lose respect for that author. Having written a few things myself (mostly fan fiction, but I've actually cashed checks for some of my writing), yes, I know it stings when people say "This sucks!" Especially when some of the criticism is unfair. But it always goes badly for the author to bite back.
Even though I'm lukewarm about his books, I love John Scalzi, because he acts like a grown-up when he gets one-star reviews. On the other hand, I recall a book I once read by Piers Anthony (yeah, yeah...) in which literally half the book was author's notes ripping up the editing comments that editors had made about a previous edition. And you thought wanky A/Ns on fanfiction.net were bad!
What do you think of snarky, biting, or mean reviews? What do you think of reviews you disagree with? What do you think of authors responding to reviews? Should reviewers be gentle in case the author actually reads the review? Or should they not care if a fragile writer gets hurt fee-fees?
The reviews I appreciate reading most are long, critical ones that talk about the good and the bad. (Or if it's all bad, at least make it funny.) I tend to skip over the reviews that say, "This was a good book I really liked the characters 4.5/5 stars can't wait to read the next book in the series kthxbai!"