Cost per new reader vs value per new reader: the two numbers that decide your ad budget

I don't come from a business background. Military, then emergency services, then this. So none of this came to me easy.

What happened was I started learning business for my own business, and working with a coach I picked up two numbers that every other industry treats as basic: cost per acquisition, and lifetime value of a customer. I used them on Weekend Publisher. Then they slowly started seeping into the work I was doing for clients.

And then I noticed something. I could barely find another book marketing coach or course talking about this. My gosh, I thought, this is the simplest thing.

Almost no coach, course, or conference talk I came across was teaching authors and publishers to work out what a reader costs and what a reader is worth. Which is strange, because it's the simplest possible way to know whether your advertising is working.

It makes a certain sense, though. Most people publishing fiction are creative people first. They came to this to write books, not to build spreadsheets. So when you ask what a new reader is worth, you often get a guess, or a shrug, or a number that's really just a feeling.

That gap is where most of the money is.

First, what counts as a new reader

A new reader is someone entering your world for the first time. In practice that means the first book in a series, or a standalone. It's the natural entry point into your ecosystem, meaning your books, your stories, your world.

Two things people get wrong here.

A Kindle Unlimited borrow counts. So does a free download. Anyone who picks up your book one for the first time is a new reader, regardless of what they paid. Whether they turn out to be a valuable new reader is a separate question, and it's the whole point of the second half of this article.

A reader is a person, not a click. This is the one I see most. Someone shows me an ad with a 10% click-through rate and tells me it's doing well.

I don't care. We could get a thousand clicks, two thousand clicks, and not a single sale. Click-through on its own doesn't mean anything. What we want to look at is conversion.

One wrinkle worth knowing. There are two kinds of series, and they behave differently.

A hard series has to be read in order. You need book one to make sense of book two. That's most of fiction.

A loose series shares a universe but follows different characters, so a reader can start anywhere. It's much less common, and in my experience it's harder to sell book three as an entry point even when it technically works. So about 99% of the time, promote book one and let read-through do the rest.

Cost per new reader: the easy half

The formula is as simple as it looks:

That "amount spent" is usually ad spend, mostly Facebook, since that's where most of the volume comes from for fiction. It can also be a paid price promotion, or anything else you put money into to get people in the door.

A realistic range is $2 to $7 across the fiction accounts I work in. It moves a bit by genre. Fantasy and science fiction tend to sit at the higher end. Romance and women's fiction tend to come in lower.

One caveat that matters more than it sounds: that band assumes people are paying for book one. If your entry book is free or 99 cents, your cost per new reader will come in well below it, and that is not the good news it appears to be. More on that in the worked example below.

Over $10 makes me wince. Not because ten dollars is automatically fatal, since a deep series with good pricing can carry it. But when I see a number that high, it usually isn't an audience problem. It's one of two things.

The first is that the ad isn't setting the right expectation. A surprising number of ads don't make it clear the reader is even clicking on a book. If they don't know what they're getting, the click is wasted the moment it happens.

The second is the book page. When someone lands there they're asking themselves two questions. Is this book any good? And will I enjoy this book?

Those are two different questions and we need to answer both of them. Reviews and a professional-looking page handle the first. Cover, blurb and category handle the second. Miss either one and we're paying for traffic that was never going to convert.

Value per new reader: the hard half

This is the number almost nobody calculates, and it's harder, so here's the actual method.

The range I see is anywhere from 30 cents to 12 dollars. That's an enormous spread, and it comes down to two things: how the books are priced, and how many of them there are.

Read-through is the engine

Read-through is the percentage of readers who finish one book and go on to the next. It's the thing that turns a single sale into a reader worth several dollars.

Two facts about it that matter more than anything else.

The drop between book one and book two is the big one. It can be anywhere from 5% to 60%, and that range is the difference between a series that scales and one that quietly bleeds money. Get past book two and read-through is usually 80% or better. Someone who read two of your books is very likely to read the rest.

How you price book one changes it. Free book ones produce the lowest read-through. Ninety-nine cent book ones do better, though still below full price. This makes sense once you think about it: the cheaper the entry, the less committed the reader, and read-through is partly a measure of whether people are finishing book one at all.

That's the other thing your read-through number tells you. If very few people are moving on, a decent number of them probably didn't finish.

How far back do you measure?

This is genuinely case by case, and anyone who gives you a fixed window is oversimplifying.

Look at only the last 90 days on a series with a recent release and you can end up showing more readers on book two than book one, which is obviously not what's happening. It's an artifact of when the books came out.

Go too wide on a series with a two-year gap between books and you'll get a read-through rate that looks terrible, when really the readers just haven't had book two available for most of the window.

So the window has to fit the release pattern. There's no single right answer.

What not to bother tracking

A reader who finishes one series and starts another of yours is real value, and I don't try to measure it.

You can't track it reliably. Unless you put a specific link in the back of the last book pointing at the next series, and even then it's not accurate. It's too far into the weeds for the precision you'd get back. Better to know it's happening, keep it in mind when you're deciding whether a series is worth finishing, and not pretend you have a number for it.

The gap is the whole business

Put the two together and the rule is simple.

When value per new reader is higher than cost per new reader, you can scale. Spend more, get more readers, make more money. That's it.

When value is far below cost and money is tight, stop spending. Not "optimise the campaign." Stop, and fix what's underneath.

People ask what ratio to aim for. I don't have one. I've never worked to one, and I'd be a bit suspicious of anyone who hands you a number here, because it comes down to your own comfort level and what else you're building at the same time.

Here's what I mean. Say we're losing a bit on every new reader. The question then is what we're getting in exchange for that. Are they following us on Amazon? Are they landing on the email list?

Because a reader on your list who you actually stay in touch with has what I'd call stored value. We've already paid to bring them in. Getting more out of them later costs us an email.

That changes the maths. A reader who cost more than they returned this month isn't necessarily a loss. They're an asset you haven't collected on yet. But only if you actually have a way to reach them again. If you don't, a loss is just a loss.

Why chasing a lower cost per reader stops working

Here's the part that surprises people.

Yes, you should work on your cost per new reader. Look at which ads are performing and which aren't, double down on the winners, cut the losers. That's the job and it's worth doing.

But there's a point of diminishing returns that arrives sooner than you'd think.

Say we're down to $2 a new reader. Maybe we can squeeze that to $1.50, $1.70. But look at what it takes to get there. Testing is volatile. While we're doing it, one ad comes in at $7 a reader, we test another one and it's $3, and we're paying those numbers for real the whole time.

So after all that noise and mess, we've probably spent way more time and paid more for each new reader than if we'd left it alone.

That's why I don't push people to go chasing that last fifty cents. The cost side has a floor and we hit it faster than we expect.

The value side doesn't have a floor, and that's where the attention should go.

Making a reader worth more

In rough order of how much they move the number:

1. Write another book. That's it. That's the biggest one and it isn't close.

It's the least clever answer on the list, and every other item here is a rounding error next to it. More books means a reader can carry further, and that goes straight into what they're worth.

2. Fix the book one to book two handoff, if it's broken. Highest leverage of the fixes, and the hardest to actually do, because the causes are usually the book itself: a slow opening, a cover promising the wrong thing, an ending that doesn't pull. Worth diagnosing before you spend another dollar. Not always worth fixing.

3. Find the most frictionless way into your world. If we've got several series, they're not going to perform the same, and the move is to send new readers down the one that's already working rather than trying to rescue the one that isn't.

I worked with an author who had four series. One was a complete bomb. Two were mediocre. One performed really well. Rather than trying to rescue the bomb, we pushed new readers toward the one that was working. Same catalogue, same ad budget, better numbers, because we stopped fighting the thing that wasn't landing.

4. Price the series as a run, not as individual books. A free or 99 cent book one buys you volume at the cost of read-through. Sometimes that's the right trade. Often it isn't, and nobody checks after the launch.

5. Make the reading order obvious. Cheap to fix, and it does nothing for a series where read-through is already 80%. But if people can't tell what comes next, some of them simply won't find out.

Why this matters more with forty books than four

Everything above scales with the size of your list, and not gently.

Value per new reader goes up as you publish more, because there's more for a reader to carry through into. And once someone finishes an entire series, something else happens: they haven't just bought into those characters, they've bought into you as a writer. That's when cross-series read-through starts working, and it's real even though I've said I don't try to measure it precisely.

Each new series doesn't just add titles. It opens up possibilities that didn't exist before, because now there's somewhere for a finished reader to go.

Which is why this maths matters more to a publisher than to a single author. Forty titles means a reader has forty chances to be worth something to you. Most operations at that scale have never worked out what that's actually worth, and are still making promo decisions one book at a time.

A worked example

An author I worked with had a four-book fantasy series. Book one was permanently free, books two through four at $4.99.

In a typical month he spent about $218 on Amazon ads and got 194 free downloads of book one. Of those, 14 went on to buy book two, 11 bought book three, and 12 bought book four. Total revenue: $160. A loss of about $60 for the month.

Run the two numbers on that:

Now look at that cost figure again. $1.12 is well below the $2 to $7 band I said was normal. By that measure the advertising was doing brilliantly.

That's the trap.

A free book is cheap to acquire readers with, because there's no decision to make. Nobody weighs up whether a free book is worth the money. So the cost per new reader drops, the ad account looks healthy, and none of it means anything, because the readers arriving that cheaply were worth 82 cents each.

Cheap readers and good readers are not the same thing. That's the entire reason we need both numbers instead of the one that's easy to measure.

So we changed the entry point. Book one went from free to $2.99 and the series moved into Kindle Unlimited.

The following month: $553 in ad spend, 660 sales, $1,332 in revenue. A profit of $779.

The cost per new reader went up, and it had to, because people now had to decide whether to spend three dollars. But the readers coming in were worth more than they cost, and that's the only comparison that matters.

If you're a publisher thinking you don't run permafree

Fair enough. The same mechanism turns up wearing different clothes.

A 99 cent launch price that nobody ever put back up. A book one discounted permanently to feed a funnel that hasn't been looked at in two years. A promo slot going to whichever title somebody happened to remember. A series that gets budget because it did well in 2023.

In every one of those the pattern is identical: someone is optimising the number that's easy to see, and nobody has worked out what the readers being bought are actually worth. The permafree version is just the clearest place to watch it happen.

Can you do this yourself?

Partly. Here's the honest split.

The easy part

Cost per new reader you can work out this afternoon. Take what you spent, take the number of book ones it moved, divide one by the other. You already have both numbers.

The doable part

For a single series, you can get a usable read-through figure by comparing units of book one against units of book two over a sensible window. It won't be precise. It will tell you whether you're looking at 10% or 50%, and that's the difference that actually changes decisions.

If you do nothing else after reading this, do that for your best-selling series this week.

Where it gets hard

Three things, and they're where most people stop.

Blending the formats. A reader can arrive through ebook, paperback, hardcover, audio, or page reads, all at different royalty rates. Rolling those into one number per reader is fiddly and easy to get subtly wrong.

Kindle Unlimited. Page reads don't arrive as readers, they arrive as pages. Turning them into "what one reader was worth" needs a conversion, and a bad conversion will quietly distort everything downstream.

Picking the window. As I said above, this is genuinely case by case. Too short on a recent release and your read-through comes out impossible. Too long on a series with a gap between books and it comes out artificially dreadful. Getting it right per series is judgment, not formula.

And then the thing that stops people even when they can do all three: running it across a whole list, every month, rather than once on one series when there's a free afternoon.

That last part is why I built KdpDeck, which does this across a full catalogue at once. It isn't something you can buy on its own at the moment, it's the tool I use when I'm doing the work for someone. But the maths above doesn't need it. Tool or no tool, the numbers are the numbers, and one series on a Saturday will tell you more than you'd think.

The point of all this

Two numbers. What a reader costs you, and what a reader is worth. The gap between them decides whether you can afford to grow.

Most people work on the first number, because it's the one that's easy to see and easy to fiddle with. The second one takes more effort to calculate and it's where nearly all the upside lives.

If you want to see how I use these on a whole list, that's here, and the Diagnostic is the fixed-price version where I run it on your own numbers.

I talked through this framework on the Hidden Gems podcast back in 2023 if you'd rather hear it than read it: How Can You Calculate the Cost Versus Value of your Readers?

Related reading: how Facebook ads campaigns actually get built, and what book marketing costs.