Updated: May 2
How do you know if your book series is profitable? Well, it involves math. Which I know a lot of you hate.
How do you figure out if a series is profitable? You need to know your book to book read-through rate, and your overall series sales through rate to see if you have a profitable series.
Why is knowing this information so important? You don't want to:
1. keep writing in a series if it isn't selling.
2. you never want to advertise a series if it isn't selling. That is throwing money away.
Let's start with book to book read-through.
First take all the sales of each book in your series...for this article we will just use ebooks. But if you have paperback and audio, you will want to do this for those as well.
The formula is simple. To figure out read-through rate from book to book.
Book 1 to 2 read-through rate (Book 2 sales/Book 1 sales) X 100
Book 2 to 3 read-through rate (Book 3 sales/Book 2 sales) X 100
Book 3 to 4 read-through rate (Book 4 sales/Book 3 sales) X 100
Book sales: Find these numbers from all of your sales platforms. Use a month or more of clean data. Preferably when you were not running any sales campaigns. It is better to use a three-month period if possible.
Book sales: Let's say these are your numbers
Book 1 = 250
Book 2 = 200
Book 3 = 190
Book 4 = 175
To find the number of readers from book 1 who read book 2:
book 1 to book 2 = (Book 2 sales/Book 1 sales) X 100
= (200/250) X 100 = 80%
book 2 to book 3 = (Book 3 sales/Book 2 sales) X 100
= (190/200) X 100 = 95%
book 3 to book 4 = (Book 4 sales/Book 3 sales) X 100
= (175/190) X 100 = 92%
Now let's calculate the series cumulative read-through. This will show us how many people who read book 1, read book 4.
To figure this one out, you take the (last book sales/first book sales) X 100.
(Using the numbers from above)
(Book 4 sales/Book 1 sales) X 100
= (175/250) X 100
= 70 X 100
That's darn good for overall series read through.
If you are in KU, there is a different formula to use:
Book 2 KU Read-through = Book 2 Pages Read/Book 1 Pages Read (repeated for other books)
However, if you are advertising this series, you really want to know what kind of money/profit you are making for every sale of book 1. Yes, you are getting a royalty rate for that book, but you need to know how much more you make for each book 1 sold based on read-through rate. You need your sales read-through rate.
Why is this important?
You want to know how much you can bid on advertisements, the highest you can bid, and still make a profit. Obviously, the higher the bid, the better chance your book is shown to potential buyers. But if you don't know the profitability of the series, you may bid too high and never make a profit off advertising.
How do you calculate sales read-through rate?
It's a relatively easy formula. The one key issue to remember, is the sales of each book are always related to book 1 in the series.
First, use a block of time that doesn't have any promotions attached to it...try and get the largest block, 3 months is good, remember you want the cleanest data.
Using the same numbers from above:
Book 1 = 250
Book 2 = 200
Book 3 = 190
Book 4 = 175
You will need your royalty rate for each book. I will use an arbitrary royalty rate for each book of 2.05 (Making it easy for this example...all books have the same royalty rate) You can find the royalty rate on your Amazon KDP dashboard.
To figure out sales read-through from book 1 to book 2
(Book 2 sales/Book 1 sales) X royalty per copy
= (200/250) X 2.05
= 0.8 X 2.05
(Book 3 sales/Book 1 sales) X royalty per copy
= (190/250) X 2.05
= 0.76 X 2.05
(Book 4 sales/Book 1 sales) X royalty per copy
= (175/250) X 2.05
= 0.7 X 2.05
Add these amounts together:
= 1.64 + 1.56 + 1.43
= $4.63 dollars in profit every time book 1 is sold.
Okay. Did that register?
Every time you sell book 1 in your series...you can assume from the formula above, and the read-through rate, that you will make an extra $4.63 on top of the royalty rate for book 1.
Now, if your numbers looked something like this:
Book 1 sales = 250
Book 2 sales = 150
Book 3 sales = 50
Book 4 sales = 20
You may have a problem with your series. Somewhere between book 2 and 3 you lost a heck of a lot of readers...actually from book 1 to 2 you took a pretty good hit. It's still profitable, but not by a lot. Especially as you get to book 4.
Does that mean you scrap the series? Not really. You may have to do a rewrite or edit of books 3 and 4. Or it may be something as simple as cover and blurb to get the readers to move forward.
My thought is, if you are losing more and more readers from book 2 to book 4, you probably have a problem with the writing...either characters, plot, overall story line...something is making your readers stop after book 2.
Before you begin advertising your series, I would suggest you calculate your book to book read-through and see if readers are moving on to the next in series. If they are, then calculate your sales read through rate.
If they are not, inspect your sales blurb and your covers. Do the covers fit the genre? Do they look like other books in that genre? What about your blurb? Is it up to par with the best-selling author's sales pitch? What are your reviews saying? Did you have the book edited?
Start with the simplest approach first. Redo the blurbs and covers...if you see changes in your sales down the line of the series, then that's all that may need to be done. If you make those changes and over time you don't see any movement in sales, it may be time look at the writing itself.
If you need to rewrite your blurb, I suggest you check out Bryan Cohen's book Sizzling Synopsis. He gives step-by-step instructions on how to craft a blurb that will hook readers and get them to buy the book from the sales page. (I used this book, and I loved it.)
I know it's hard to face the fact that your series, your baby, may not be profitable. However, you don't want to keep writing something that isn't making you money. If you have lack luster read through/sales read through, you need to find out if you can fix the problem. You can't bury your head in the sand and hope it gets better. That will do nothing for you or your writing career.