Kindle Unlimited has revolutionized the eBook experience for both readers and authors. Last year we took a look at how Kindle Unlimited affects authors and publishers. This year we want to take a closer look at the habits of KU readers compared to non-KU readers, and what that means for authors whose titles are enrolled in KU. We surveyed almost 1,000 readers and analyzed the results to find out what the takeaways are for the author community.

1. How does Kindle Unlimited work for the subscriber?

To start with the basics: Kindle Unlimited is a subscription service that allows readers to read the books available as part of the Kindle Unlimited library for “free” (think Netflix for books). The service currently costs $9.99/ month, and there are over 1.4 million titles available to enjoy. Most of the books available are either classics or titles published through Amazon imprints and Kindle Direct Publishing. This means that if, as a reader, you most frequently read titles by popular, best-selling authors, you may not find the names you recognize available in the KU library. To date, none of the major publishers have opted to make their titles available through KU.

KU readers can read as many books as they want per month. The one limitation is that readers can only have 10 Kindle Unlimited books downloaded to their devices at a time. This means that readers can’t “hoard” books the way that they may normally feel inclined to. When a subscriber is in the Kindle Store, whether it’s in the Amazon app, the Kindle app, or the Amazon website, they can see clearly which titles are available as part of their subscription.

2. How many Kindle Unlimited Subscribers are there?

Amazon has never publicized the total number of subscribers in KU. However, we do have some information about the KU program, and we can use our available data to estimate the total number of KU subscribers. We recently wrote an article on Kindle Unlimited Royalties where we have data points for the KDP Global Fund and the KENP payout rate. When you divide the global fund by the payout by KENP payout, you get the total number of pages read in KU for a given month.

For this exercise let’s use the data from February 2017. The Fund was $16.8 million and the payout per KENP was about $0.005.

KDP Global Fund / KENP Payout = Total number of Pages read in the month on KU

16,800,000 / 0.005 = 3,360,000,000

That’s over 3 billion pages read! If we assume the average novel is 250 pages, we can back into the number of novels read: 3,360,000,000 divided by 250 gives you 12,440,000 average length novels read through KU subscriptions per month.

Based on our survey data, KU subscribers read about 5 books per month. We can use this data to estimate a subscriber count for KU.

Number of KU Novels Read / Number of Novels read by one Subscriber = Total Number of Subscribers

12,440,000 / 5 = 2,488,000 KU subscribers

2.5 million readers in KU is a lot of readers, and because our calculations are based on pages read it’s likely that the 2.5 Million number represents the active readers enrolled in KU. We would guess there are even more inactive users who are subscribed but are not reading. There are limitations with our data, and we’re making quite a few educated assumptions but we think it’s safe to assume that there at least 3 million readers in Amazon’s Kindle Unlimited.

3. How many books does a KU subscriber read?

When we asked KU readers how many titles they read per month, one thing became apparent very quickly: Kindle Unlimited is filled of avid readers. Over 71% of KU subscribers read 5 books per month or more. Compare that to non-KU readers, where only 57% of readers read 5 books per month or more. That makes sense since KU subscribers pay $9.99 per month for the service, there is an incentive to get your money’s worth. Also, people who read a lot of books will get the most value from KU as they were likely spending more than $9.99 per month purchasing books. 20% of our KU subscriber sample said they read more than 20 books per month!


 4. Do Kindle Unlimited Subscribers review titles, and when they do, do they count as verified?

When we asked our readers how often they reviewed the books they read, KU subscribers were more likely to leave a review than non-KU readers. 27% of KU subscribers review books somewhat often or very often, compared to Non-KU readers who review often or somewhat often only 20% of the time.

Reviews left by Kindle Unlimited subscribers do not show as verified reviews on Amazon. However, even if KU readers’ reviews don’t have the “verified” sticker on them, they still count toward your total review count and rank, so they are beneficial.


5. Do Kindle Unlimited Subscribers purchase books outside of the KU Library?

Yes! 77% of KU subscribers say that they still purchase books even if those books are not in KU. This means that if an author has a reader following in KU, then chooses to remove their books from KU, they are not alienating their KU readers. There is a high chance that those readers will continue to read and pay for their books.

6. What genres do Kindle Unlimited subscribers read?

We noticed that the genre popularity with KU readers mirrors the genre popularity amongst readers at large, with two notable exceptions.

First: Romance, Fantasy, and Mystery are the most popular genres for both KU and Non-KU readers. However, we noticed a heavier emphasis on Romance within the KU Readers, with 35% of KU readers citing Romance as their primary genre compared to 25% of Non-KU readers. This makes sense to us, as Romance readers are generally avid readers who consume multiple books per week, so KU makes sense for them. Romance authors who do not have a book enrolled in KU may want to consider it since over a third of KU readers enjoy Romance. Having a title available through KU is a targeted way to get in front of a group of readers who are predisposed to like Romance.

Second: We also noticed that Non-KU readers read more Mysteries, with about 17% of Non-KU readers citing Mystery as their primary genre compared to 10% of KU readers. We have a hunch that many Mystery readers feel loyalty to the best-selling authors (Patterson, Baldacci, etc.), whose titles are not available through KU, making Mystery readers less likely to subscribe.

7. Which type of Devices do Kindle Unlimited Subscribers read on?

Before we get into the differences between KU readers and Non-KU readers devices, let’s talk about the overall picture of reading preferences that came out of the survey. We were surprised to find that almost 75% of surveyed readers are reading on a phone or a tablet! This is important because modern phones and tablets all have a full internet browser and color screens. For authors, this is an extremely important finding for a few reasons.

  1. ‘Back matter’ or ‘front matter’ links will work very well on those devices because they have full browsers built in.
    That means adding a join the mailing list link in your book will allow the user to tap on it directly and join your list easily. With older Kindle devices, the ‘experimental browser’ is fairly limited and not reliable enough to collect emails well. The era of reader interactivity is upon us.
  2. It places additional weight on cover design.
    Now that the shopping experience will be mostly presented in color it’s even more important to have a professionally designed cover.
  3. It opens the door for certain image-heavy genres.
    This is really great for any genre that relies on imagery, for example: cookbooks, graphic novels, and children’s books. It may also allow for genres that were traditionally text-centric to make more use of color photos or audio snippets. Perhaps Fantasy authors with elaborate fictional worlds could offer pronunciation guides or colored maps. We’re excited to see how authors push the boundaries of multimedia now that the reading technology can support it.

Alright, but back to Kindle Unlimited. Do KU Readers have different device preferences? They do. KU readers are more likely to have a Kindle Branded tablet (Kindle Fire) vs. the Kindle app on a tablet or phone.


8. How many titles on the top charts are enrolled in Kindle Unlimited?

On the day that we checked (3/28/17), 60% of the best selling titles on the Amazon paid charts were enrolled in KU. With 88% of the romances, 76% of the fantasy, and 58% of the Mystery/Thriller titles being available through KU.

On the free charts, it’s a slightly different story. Only 41% of the top 100 books are in KU, with only 24% of romances, 14% of Fantasy, and 28% of mystery best selling free titles being enrolled. We believe that the difference between KU percentages on the free and paid charts are due to Amazon’s KDP rules. When your book is in KU, your ability to price the book at Free is limited to 5 days per quarter, which limits the an author’s ability to leverage free days as a marketing tactic.

% of the Top 100 Books that are in KU
% of the Top 100 Books that are in KU
All Genres 60%  41%
Romance 88%  24%
Fantasy 76%  14%
Mystery / Thriller 58% 28%

Since we pulled this data on a specific day these percentages are likely to jump around a bit, but this is a good snapshot for comparison.

9. What can Authors Expect?

There are a few main takeaways from all of the graphs above that we want to leave you with:

  • The KDP fund just keeps growing. Month over month the KDP fund gets bigger, which means that plenty of readers are actively reading the enrolled titles. If you can sell your book to this audience, then you’ll get a portion of that pot. The growth of KU means it’s here to stay, it’s no longer an experiment.
  • Romance authors benefit greatly from KU.  It’s hard to argue with the fact that 88 of the top 100 romance books on the bestseller charts were enrolled in KU. Romance readers are avid, and will gladly read through enough books in a month to make the $9.99 subscription fee worth it.
  • KU readers are incredibly active. KU readers read more books and review books at a higher rate. It’s safe to assume they are more active generally than their Non-KU counterparts.
  • You can use KU enrollment strategically. There is an opportunity to use KU enrollment as a strategy to acquire readers who then purchase your other books. If 77% of KU subscribers go on to purchase books outside of the program, then one reader acquisition strategy is to put some titles in KU, allowing those readers to read them for “free”, and then converting those readers into paying customers on your other titles.

Are your titles in KU? What has your experience been? We know that authors have to consider the pros and cons of KDP Select when deciding whether to enroll. Which side are you on?  Let us know your story in the comments!

A Note on Methodology

The following conclusions are based off of self-reported survey results from our author base. We did no heavy statistical analysis on the data, but rather took the raw data, cleaned it up, and made some logical inferences from what we saw. If you are a crazy market research pro, or a stats geek, please try not to hyperventilate.

*A previous version of this post claimed that KU readers’ reviews count as verified. That was incorrect. You can read Amazon’s official language around verified reviews here.*  

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