How to Calculate Series Read-Through (And Why It’s Important to Know)

This is not the most riveting topic out there, but understanding series read-through is something that any writer who is planning to create (or is in the process of creating) a series needs to understand. If you don’t have a solid grasp on whether or not readers are picking up the next book in your series, you don’t know if it’s worth carrying on with it — nor do you know what sort of advertising margins you need to maintain.

These are some weighty topics, so I’ll tackle them one at a time. First off, let’s dig into what read-through is and discuss its two flavors.

The basic distinction is sales versus Kindle Unlimited (KU) reads. You’re going to find that KU readers tend to read through a series at a higher rate than buyers. The primary reason for this is they don’t have to pay for the next book, and also because they are typically more voracious, consuming every book in their path like some sort of word-devouring space monster.

Yeah, I’m a Sci-Fi author. I can’t help it.

Do I Really Have to Calculate Things?

I know…writing books isn’t supposed to involve math, and I’m sorry. But if you’re an indie, you’re now a small business owner, and you have to understand how well your products are selling, what sorts of marketing efforts are profitable, and if there are any quality issues in your product.

Yuck. So clinical. Still, it’s something we all have to do. I’ll do my best to make it fun.

As is often the case when you’re creating something, you spend both time and money to produce the work. Your time has a cost. If you’re writing a series that is dying on the vine when you could be writing a series that would sell better, that time spent on the low-performing series has a cost.

Of course, the money you pay for covers and edits on a series has a cost, as does the money you spend advertising the books. These things add up, so if there are problems with your series read-through, you need to know.

Also, knowing your read-through can help you understand both how to price Book 1 and what CPC (cost per click) on ads is profitable (this applies to Facebook, AMS ads, and BookBub ads).

This is important stuff, so let’s dig in!

In this article, you will learn:

• How to calculate series sell-through
• How to calculate KU series read-through
• Benchmarks for measuring success
• How to know if your series ads are profitable
• Tips on how to price your books in response to your findings

Calculating Series Sell-Through

Some people call non-KU read-through “sell-through,” so we’ll use that when talking about book sales to keep things simple for this article.

Your series sell-through is pretty easy to calculate. Take the sales of the last book in your series and divide that number by the sales of Book 1.

Let’s say you sold 428 copies of Book 1, and 247 copies of Book 2. That gives us:

247 ÷ 428 = 57.7%

That’s your total series read-through, and to be honest, read-through over 50% for anything longer than three books is not bad at all.

(Don’t worry about having to do this all by hand, I’ll point you toward some tools to help at the end.)

Many authors see something in the neighborhood of 50-60% from books 1 to 2. Unless you’re writing a more loosely connected series, the read-through from the first to the second book is very important. If it’s less than 50%, there’s a problem you need to address.

What is that problem? Chances are the reviews of Book 1 will tell you the answer. Gird your loins, you’re going to need to read some 1 – 3 Stars to get a picture of why readers didn’t carry on.

This is a look at a single month’s sales using 100 reads of Book 1, which makes this very easy to follow. What you’ll notice is that, as the series progresses, the book-on-book sell-through (from one book to the next) goes up. This is expected, and when you plug in your numbers, you should see a similar pattern—unless a book was recently released.

Calculating KU Series Read-Through

Kindle Unlimited read-through is a bit harder to work out because you don’t know for sure if someone read all of a given book since Amazon only reports pages read, not the percentage of the book read.

Making it more difficult, those KU “pages” don’t correlate to any other page count for your books. However, it is possible to find out what KENPC (Kindle Edition Normalized Page Count) your book has.

One method is to go to the KDP Select Info section for the book in your dashboard and get the KENPC (you have to do this for each book).

Near the bottom of the page, you’ll see the page count.

Once you have this information in hand for each book, you’ll need to divide your KU pages read by this number to get your total books read for the date range you’re examining.

BookReport will also show you the KENPC on the page where you see your book info.

As an example, if the book in question had 91,303 “KU Page reads” reported, then the total reads would be:

Full Reads: 91303 ÷ 402 = 227

If you use BookReport, it can tell you what your “full reads” are as well. BookReport calls it “~Borrows” and you can enable it as a column on your report.

KU, however, presents a unique problem: we don’t know if someone read the entire book! However, I’ll show you why this really isn’t an issue.

Let’s say that the page reads for Book 1 work out to 227 full copies read, and for Book 2, they work out to 196 full copies.

227 ÷ 196 = 86.3%

You’ll find that this sort of read-through percentage from Book 1 to 2 is normal for KU. I would consider 75% to be low when it comes to a KU book that has found its audience—which is to say that if it is lower than 75%, the book has an issue or it’s not being marketed to the right audience.

Of course, for all we know, it’s likely that a percentage of people who started reading Book 1 never finished, and it really wasn’t 227 full reads, but probably something more like 175 partial reads and 150 full reads (maybe…we have no way of knowing).

But here’s the thing: it doesn’t matter.

Because (assuming your series is meant to be read in order, and you haven’t heavily marketed Book 2) we can surmise that the vast majority of people who read Book 2 first read Book 1. This means, even if we don’t know the exact number of people who read Book 1, we do know how well it’s feeding readers into Book 2.

Exceptions to the ‘Book 2' 50% (75% in KU) Rule

Of course, we can’t have a rule without an exception…or three.

There are a number of scenarios that can drastically affect your Book 1 to 2 sell-through. The first is if you are giving away Book 1 for free. In that case, you should be expecting something closer to 3 – 6% when it comes to people who read Book 1 and go on to buy Book 2.

Another exception is release timing. If Book 1 has been out for years and Book 2 is just a few months old, you can’t expect the sell-through to have caught up. Depending on the timing, you may need to take a smaller slice and only look at the past few months.

Box sets can throw this off as well. If a box set doesn’t contain all the books in a series, add it and Book 1’s sales together, and then divide by the sales of the last book in the series:

319 ÷ (428 + 131) = 57.1%

(last book divided by book 1 + box set sales)

The last exception is price. Dang…that’s four.

Price has several considerations. First, is the price difference between books? If Book 1 is $2.99 and Book 2 is $4.99, that increase will cause some people who are on the fence to not pick up Book 2. Conversely, if Book 1 is $4.99 and Book 2 is $2.99, people may be put off, thinking it is a shorter story. That second scenario is pretty rare. Whenever I’ve seen it, the second book is a lot shorter—which is an issue, but one that’s outside the scope of this article.

A 99c first-in-series can have a similar effect on sell-through. What you may see in this case is that a lot of people buy Book 1 on a lark and either never read it or find that it isn’t their cup of tea. A full-price Book 1 will be more likely to attract people who are squarely in your desired readership, thus keeping them going through the series.

In addition, you might also find that some KU readers will buy the first book at 99c and then switch to KU for Book 2. This is usually a small percentage, though.

It’s normal to see sell-through that is 10-30% lower when Book 1 is at 99c versus full price.

Also, if you’ve changed prices during your book’s history, you’ll need to select date ranges where they did not change for the best results. Keep in mind, however, not everyone reads books quickly or right when they get them, so this is not an exact science.

Note: At the end, I’ll show you how to use your read-through to determine the best price for Book 1 in your series.

Knowing If Your Ads Are Profitable

Now that you know what your read-through looks like, you can figure out how much money you make with every sale of Book 1 in your series.

This is done by simply calculating the percentage of people who read-through book-by-book. You can do this on your own, or you can use a spreadsheet linked at the end of the article. ReaderLinks can do this for you as well.

Let’s say that you sell Book 1 at 99c, and with your read-through on a 5-book series, you average $12 (once the readers have completed the series) each time you sell that first book.

Now, let’s say you’re running an ad with a 30c cost per click. A good assumption to start with is that you’re getting one sale for every 30 clicks. If you multiply your ratio (1 in 30) by the cost per click ($0.30), you get the cost per sale of Book 1.

$0.30 x 30 = $9.00

That’s a little alarming! That’s spending $9 to make $12. It’s in the black but not by a lot. However, you know your threshold. If those clicks get over 30c, the ad might not be profitable anymore.

Let’s see what this looks like if you can get a lower CPC on your ads, as well as a better conversion:

$0.15 x 20 = $3.00

Look at that! A small improvement to conversion, and halving the cost per click, brought the cost to sell Book 1 down to $3.00! Now we’re looking at 300% ROI!

Just to be clear, the “conversion” I’m referring to is a sale on the retail site (such as Amazon). You can’t know for sure what sort of conversions you’re getting, so you have to use things like affiliate codes to guess.

If you’re getting a lot of clicks, but not a lot of sales, then the problem you’re facing is that the product page isn’t compelling to the people you’re sending there.

Figuring Out How to Price Book 1

I bet you didn’t think you’d get advice on this topic in this article (aside from when I told you at the outset), but here it is! How can we tell what a good Book 1 price is? Through the power of math, that’s how!

Two things come into play when pricing Book 1. It affects the ease of selling said book, and it also affects read-through. Let’s say, for example, that when Book 1 is at 99c, you sell 10 a day.

You’re running ads, and your cost per click is $0.20 and your conversion is 1:20 (5%). This means it costs you $4 to sell Book 1.

A sale of Book 1 earns you 35c in royalties. Let’s say that the series is three books long, and Books 2 and 3 are at $3.99. That means you’ll net about $2.70 in royalties for the sale of each one.

We’ll assume that 65% of the people who read Book 1 go on to read Book 2, and 85% of the people who read Book 2 go on to read Book 3. Here we go.

10 sales of Book 1 at $0.35ea in royalty:

10 x $0.35 = $3.50

65% sell-through to Book 2 is 6.5 sales at $2.70ea in royalty:

10 x .65 x $2.70 = $17.55

85% sell-through to Book 3 is 5.53 sales at $2.70ea in royalty:

6.5 x .85 x $2.70 = $14.72

Total: $35.77

If we have a cost per click of $0.20 and one in twenty people buy, then it costs $4 to sell each copy of Book 1 and $40 to sell all ten. We can then calculate our profit.

Profit: $35.77 – $40.00 = -$4.23
(22 books sold)

Uh oh! We’re losing money here! Fear not, all is not lost. In a scenario where there is a fourth book, this would be profitable, and if the book is in KU, it would likely be making $25 to $30 in addition, so it would be a net win.

Now, let’s take those same numbers and adjust them for a full-price Book 1. Keep in mind that, so long as you’re not mentioning price in your ads, the cost per click is not affected by this. However, the sales conversion will be. It’ll get worse, while the sell-through after Book 1 will get better.

7 sales of Book 1 at $2.70ea in royalty:

7 x $2.70 = $18.90

75% sell-through to Book 2 is 5.25 sales at $2.70ea in royalty:

7 x .75 x $2.70 = $14.16

85% sell-through to Book 3 is 4.46 sales at $2.70ea in royalty:

5.25 x .85 x $2.70 = $12.01

Total: $45.07

If our cost per click holds steady at 20c, but our conversion increases to 1:25, we see a cost of $5 to sell each Book 1. In this example, we sold 7 — so our total cost of sale for those first books was $35. However, we made more money than the first example, and as you can see below, a higher profit.

Profit: $45.07 – $35.00 = $10.07

(16.7 books sold)

In this scenario, the author sold five fewer books, but made $14 more! (And a profit.) That’s not to say this always works out in favor of the higher-priced Book 1. Often, in longer-running series with good sell-through, you’ll see that a lower-priced Book 1 wins.

Either way, you can use this to tell which pricing strategy will be more profitable for you. Or, if you want to make a change, you’ll know what your read-through needs to be in order to make more money than your previous pricing strategy did.

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Now You Have the Power!

So, now that you have the supreme power of knowing what your read-through is, it’s time to take a look at yours and see what it tells you.

Can you increase the price of Book 1? Should you decrease it instead? Are your ads profitable? Did you make a mistake in Book 2, and no one is following on to Book 3?

You may have to do a bit of experimenting, but your numbers will tell you the right strategy.

If you would like to download the spreadsheet I made to help calculate read-through, you can get it here.

And if you’d like to learn more about this topic, as well as how to up your game with ads and marketing, check out our books here.