I’ve seen people talk about the number of reviews on Amazon that can somehow trigger the “amazon algorithm” to start promoting your book.

Some debunking is in order.

This is my takeaway from the below article by Cate Baum:

Amazon will promote your book whenever it thinks it has a chance to make money. If a customer previously bought one of your books, they might show him the next one – even if it doesn’t have any reviews.

The algorithm really isn’t all that secret. It’s only about making sales. Amazon makes open recommendations to authors / publishers, and those are aimed at making their books more discoverable and sell more copies.

Amazon WANTS you to sell, because that’s how they make money. All it comes down to, is – which is more likely to generate a sale: your or a competing book? So if you make things easy for Amazon (by working with their guidelines), everybody will win.

For all my author friends, I really suggest you read this article in full: Mythbusting The Amazon Algorithm – Reviews and Ranking For Authors:

Despite many educated guesses that seem to have passed into urban legend in self-publishing communities online, there are no secrets to the Amazon ranking system.

I have spent the last few months tracking down programmers, algorithm experts, and reading technical documentation about Amazon’s algorithm, and the documentation that is provided online by Amazon at Amazon Seller Central and KDP. What I didn’t do was talk to any authors or bloggers, because that seems to be where the myths are coming from.
My first takehome fact for authors is that Amazon’s ranking is not a great mystery that authors must slave over to “hack” into showing books in ranking. There are no “secret” ways to “trick” Amazon. If this is all a bit technical for you and you just want to make your book page work, I have summarized conclusions and action points at the end of the article.

— Cate Baum, former search expert and COO of SPR

And the continuation about Mythbusting The Amazon Algorithm Part II: Amazon Lists, Products, and Sales.

Really, read it. It will make you sleep better at night, and help you concentrate on what’s important in writing and publishing.

EDIT: Robert Lee Beers has pointed out to me some rebuttal comments on this KDP forum post. While they do raise some valid points (Self Publishing Review is not independent entity, they make their business through reviews), I have seen as well that Amazon will put books on the ‘also bought’ line well before they have 50 reviews (Dan Buri has sent me a screenshot).

However I feel that the objections raised do not invalidate that Amazon treats relevance somewhat different than ranking. It might show your book to a prospective buyer, if it thinks it will make a sale. While overall number of reviews (and other factors) help push your book to the front, there is no magical 50 that kicks off the process.

I feel that, despite possible bias, there is more good in this article than otherwise.