Seriously, you can’t.
The value of any book’s average-review rating is psychological in nature. We’ve been conditioned to believe a book that has a 3-star or below average is a terrible book. It’s not true, but it’s the perceived value of the book. In getting my Psychology degree, I was exposed to studies that showed how real the “group think” phenomenon is. We all like to think that we’re independent thinkers who aren’t impacted by what other people say and do, but the truth is, we are greatly impacted by what others are saying and doing. A person has to be intentional in order to think independently. This is why reviews are so powerful in the world of books. In only one second, we form an opinion of a book simply by the average number of stars it has.
The trouble is, it’s easy to manipulate the book review system. I’ll give some real world examples below.
Reasons for fake 1 and 2-star reviews:
Back January of this year, a group of scammers on Goodreads sent out messages to some authors basically saying, “If you don’t buy our review service, we’ll go in and 1-star your books.” When the author didn’t pay, the scammers used fake accounts and did as promised. A few authors reported getting 30 1-star reviews in one day. Sure, if a reader were to dig in and take a look at the reviews, they would probably realize the author was a victim of a scam, but most readers don’t look beyond that snapshot “average star rating” that is placed right next to the book. Most readers would assume the book truly sucks and keep scrolling through books. The scammers know this, which is why they followed through with the threat. You can read about this in detail at this post. I never go to Goodreads, so I found out about this recently. Fortunately, enough authors went to Goodreads about it. (It takes a significant number of authors complaining to get things done.) From a casual search I did on Goodreads, it looks like Goodreads has resolved this issue. The authors were able to win over the scammers.
I only mention the thing about Goodreads to demonstrate how easy it is for anyone to create fake accounts with the intention of leaving 1 and 2-star reviews on someone’s books. Now, the scammers on Goodreads were looking to make a quick buck off of the fear of authors. In the author community, reviews are important. Retailers tend to offer preferential treatment to higher-starred books, and advertising companies won’t promote books unless those books have a certain amount of 5-star reviews. So whether we want to admit it or not, reviews matter.
People have other motives to try to hurt an author via the review than to make a quick buck. People who don’t like an author in real life have been known to leave nasty reviews on books out of spite. I remember hearing from an author years ago whose ex-wife made it a point to 1-star every book he put out with the intention of killing his author career. No amount of telling Amazon about those reviews got them removed.
Also, there are authors who’ve gotten 1 or 2-star reviews as soon as their books are released. It’s not the fact that those reviews popped up so quickly that is the red flag. The red flag is the fact that this happens to multiple books. One author said that she was seeing a trend where one person kept buying her books (for a verified purchase tag on Amazon), 1-starring the book, and within the same day returning the book. This happened to every single book in her series by the same reviewer within a week. I find it difficult to believe that the reviewer was sincere about giving any of her books a chance. The reviewer obviously had ulterior motives. And this happens quite a bit in the author community to other authors. I have dealt with this myself.
Also, sometimes books get a 1 or 2-star rating from other authors whose goal is to hurt their competitor. The author leaving the review doesn’t want the book to be successful (for whatever reason). I’d like to say every author in the community is supportive and encouraging, but this simply isn’t true. Authors do use reviews to hurt other authors. I’ll use myself as an example this time. Back around the 2009-2011 time period, there was a certain reviewer who made it a point to 1 and 2-star my books. It turns out she wrote in the same genre I did under a pen name. So when she was in the groups, she was known as X, but when her books said she was Y. This hid her real identify. The problem is that it’s a small world, and someone connected the dots and exposed her for being an author who was pretending to only be a reader. (A word of advice, if you are an author, you can participate in a reader community, but be honest about being an author AND resist the impulse to use the community to market your books. If you’re in a reader group, be there as a reader.)
I spent a lot of time talking about the low-star reviews, but there is the other side of the equation. Not all reviews are manipulated to hurt books.
Reasons for fake 4 and 5-star reviews:
Sometimes the system is rigged in favor of amassing favorable reviews. I remember talking to a writer in one of my writing groups who admitted to paying a review service to give her books glowing reviews because she was struggling to get visibility. She also happened to be paid for leaving glowing reviews on other authors’ books. Then there was another author who was later exposed for paying for reviews on his books. It was a big deal back in the early 2010s in the writing community. He got publicly shamed for this. I don’t know if it ended up hurting his career or not. All I know is that I learned this is a huge “no-no” in the author community.
Then there are authors and friends who 5-star each other’s books for the sole purpose of “boosting” the average star rating on a book. I should add a disclaimer here. I have no trouble with authors reviewing each other’s books as long as the authors give an honest review. If the author truly loves a book, they should be able to say so. The problem comes when authors are leaving glowing reviews just to boost the book’s reviews. Some authors don’t even read the book. They just throw out the 4 or 5-star review on the book. I have left reviews, but I only do it on books I’ve liked. I don’t want to be the author who trashes another author’s books. I do, however, aim to give my honest opinion. Over the years, I have become less and less inclined to leave a review. We’re currently in an atmosphere where authors leaving reviews can do more harm to an author’s book than will help. This is because readers tend not to trust those reviews. The best reviews are those by people who don’t write books.
Now, I will add, that authors should have free reign to review books dedicated specifically to authors. Writing craft books or marketing books are perfect for authors to review, regardless of how the authors feel about the book. If I’m going to invest my time and money into a writing or marketing book, I want to know if it’s worth it. I want the good, the bad, and the ugly in the review.
But for fiction, I think authors are better off raising other authors up, and my advice is that if you don’t like the book, don’t review it. This world would be a much better place if we all lived by the adage, “Treat others as you’d want to be treated.” I can’t think of a single author who would love it if another author left a low-star rating on their book. So why do that to someone else’s book? Let the readers take care of the fiction that’s out there. If the reader honestly doesn’t like the book, they can say it.
So let’s say you come across a book, but you’re wondering about the reviews. Can the reviews be trusted at all? I have a couple of tips to help in this regard.
1. Check the author’s history. What other books have they done? How long have they been around?
2. The best reviews are those where the reviewer gives you specific examples of what happens in the book AND their opinion. If the reviewer can tell you something that happened in the book and what they thought about it, then you’re almost certain that this is a legitimate review. Obviously, someone could get the cliff notes from someone about the story, but most people don’t take the time to go into detail about the books unless they’ve actually read the book.
3. Check the sample for yourself. The sample isn’t the entire book, but it should give you enough to decide if the book is something that you might enjoy. Ultimately, your satisfaction (or dissatisfaction) with a book is based on your own tastes, not someone else’s.
Ruth Ann Nordin's Author Blog 
You make some really excellent points here. I agree with everything. I also never leave a bad review whether it’s a book or restaurant because I believe if I “don’t have something nice to say I should say nothing at all.” I will hit the stars when I really like a book though. I like to judge a book myself. If the synopsis sounds like something I would like, I get at least a sample, or just take a chance and buy the book. Over the years there have been very few books that I would have considered a dud to me.
I will sometimes read reviews, but don’t rely on them totally. I once bought a book because it was on the best seller list but never finished it because it just wasn’t for me.
That being said there was a time I decided to give a book a try that I didn’t think I would like at all and turned out loving it and couldn’t wait to read all the books in the series. You just never know.
I’m sorry that there is so much meanness in the publishing world that people feel they need to knock the other guy down. Seems to happen too much in this world.
Stay strong and true, and thanks for writing.
You have made a lot of excellent points. It really does boil down to a book being in the “eye of the beholder”, isn’t it? Unless we give something a try, we don’t know if it’ll be something we enjoy.
Like you, I don’t leave a bad review on restaurants or other things, either. I prefer to leave feedback when it’s positive. I figure the world has enough bad in it. I want to be the person that makes someone smile.
I think what surprised me the most in the publishing business is that authors will sometimes go after other authors. I had this vision that as authors, we’d all want to support and encourage each other because we all loved to write. Most authors are great, and for that, I’m grateful.
I had a bad review on one of my books one time that actually said things that were not true. People were like “did you review the wrong book?” (I’m thankful for those comments.) I think some reviewers like to be nasty. I’ve heard of authors giving other authors bad reviews, too. I’ve suspected some of my bad reviews weren’t true reviews just based on what they said. This was all on my other pen name.
What’s your other pen name? I wonder if I have any of those books?
Catherine Lynn, that’s a great point I didn’t think about. Sometimes people review the wrong book. I remember an author who got a 1-star review on her book from a reviewer who said she had bought the entire series and wasn’t sure about reading Book 2. This author hadn’t even written Book 2 at the time of the review, so that’s how she knew the review was for the wrong book.
I am with the majority of these reviewer reviews. I figure if I completely read the book, it more than likely deserves at least a 3 Star view…and explain why not more. i.e. My biggest pet peeve is when the author writes a great book, but their proofreader let too many bloopers go unnoticed.
Number one pet peeve is the word “rain” that means it is wet outside. Rein means that I need to get that horse out of the rain. And I consider Reign belongs to the authors of the books, because they are the kings and queens of the story!
The proofreader thing is tricky because it’s possible the proofreader did point out errors but the author didn’t fix them. On the other hand, you have the scenario where the proofreaders and authors didn’t catch everything. I’ve had multiple proofreaders go over my books in the past, and none catch all of the errors. Sadly, even though I go through the book after they’re done, there’s usually something that slips past me, too. It’s too easy to read what should be there. It’s extremely frustrating.
I don’t trust the “poorly edited” reviews unless I go into the sample and see it for myself. In the past, I’ve had emails from a few people who said my book is poorly edited. When I asked them what they meant, the issue had to do with commas. It turns out they were wrong. Basically, they were insistent that I do the following with my books:
1. The day was windy, I closed the door. (I don’t know why they don’t realize those two sentences should be separated by a period, but they are adamant that I should use a comma.)
2. I went to the beach, and sat on a towel. (Putting a comma there is wrong unless I were to put in a word like “and” followed by a subject. Ironically, these seem to be the same people who believe in the #1 comma usage.)
I don’t mind someone pointing out an error where I actually messed up, but when people come to my inbox with complaints that I need an editor, it annoys me. I wish these people would at least take the time to do a Google search on grammar rules before they criticize my editing.
I liked what you did with the “rain, rein, reign” words.
My pet peeve is “loose” vs “lose”. I can’t tell you how many times people “loose” their minds. Just typing that makes my eyes go buggy.