August 8th, 2026   •   4 minute read   •   Issue #166

There's a number in Facebook Ads Manager that most authors watch obsessively.

Cost per click.

You'll see it posted in Facebook groups and forums. "Down to $0.12!" "Under 10 cents!" "Cracked it!"

And I get it.

It's a clean, simple number that goes up or down, and up feels bad and down feels good, and after a few weeks of running ads it becomes the number you check first when you open Ads Manager.

Here's the problem though. CPC is a vanity metric.

It tells you very little about whether the ad is doing the job you want it, driving sales.

It tells you one thing: how cheap it is to persuade someone on Facebook to move their thumb an inch and tap through to your book on Amazon.

Whether that tap turns into a sale, a page read, a full read-through of the series, or nothing at all, CPC has nothing to say about.

I've watched authors optimize their entire campaign strategy around dropping their CPC by two cents, and be genuinely thrilled when they get there, while the number that actually pays their mortgage sits in their KDP dashboard, getting worse.

Let me show you what I mean.

The trap of the cheap click

Two ads. Same book. Same budget.

Ad A gets clicks at $0.11
Ad B gets clicks at $0.22

If you're watching CPC, Ad A is the obvious winner. You turn off Ad B. You put more budget behind Ad A. You feel like you're doing your job.

But look at what happened downstream. Ad A produced two sales that week. Ad B produced eleven.

Ad A's clickers were curious, cheap to reach, but had no intention of buying.

Ad B's clickers cost more, but the ones who tapped through actually wanted the book. Per dollar spent, Ad B was more than twice as profitable, and you just turned it off because a number you shouldn't have been optimizing for went the wrong way.

This isn't a hypothetical. It's the most common self-inflicted wound I see when I look at an author's ad account for the first time.

Where CPC does matter (a bit)

If your cost per unique outbound click is creeping past $0.50 on a Traffic ad, that is a signal worth listening to. Not a verdict, a signal.

Nine times out of ten it means the creative isn't landing. The image isn't stopping the scroll, or the copy isn't giving the right reader a reason to tap.

But even that is context-dependent.

If a $0.50-click ad is driving plenty of sales each week and doing it profitably, you leave it alone. CPC is a diagnostic, not a scoreboard. It can tell you where to look. It can't tell you whether the ad is working.

The number to look at instead

Facebook doesn't know whether your ads sold books. There is no pixel firing on the Kindle store. 

What you need is Amazon Attribution, a free tool from Amazon that gives every ad its own tracking tag, then reports back on the sales and page reads that tag drove.

If you're not using it, that's the single most valuable afternoon you can spend this month.

One caveat about Amazon Attribution.

It's not foolproof. In my own accounts and my clients' accounts, sales come back roughly 70-80% accurate. Page reads are rougher again, closer to 30-40%. Treat the Attribution numbers as the best signal you've got, not as gospel.

Once you've got them, you can calculate conversion rate and cost-per-sale for each ad. Those figures give you a rough sense of your winners and losers, and that's genuinely useful, but it's not a true reflection of performance.

What it gives you is the closest signal you'll get at the ad level, and it's miles better than staring at CPC.

The number I actually pay most attention to, though, is even simpler.

It's how much the ads spent this month overall, and how much came back in royalties, and the gap between the two.

That gap is your profit, and it's the only number in this entire discussion that pays for anything.

If you're spending $100 a day on Facebook ads and earning $100 a day in royalties, you don't have an ads strategy. You have a very expensive hobby.

What to do this week

Three things.

First, set up Amazon Attribution if you haven't already, and give every ad its own tag so you can see which ones are driving activity. That's the one non-negotiable.

Second, for a Traffic ad, these are the columns I actually look at in Facebook Ads Manager:

→ Amount spent
→ Unique outbound clicks
→ Cost per unique outbound click
→ Unique outbound CTR
→ CPM
→ Frequency

Those are the numbers Facebook is qualified to tell you. Watch them to spot creative problems, not to judge whether the ads are working.

Third, a three-minute-a-day habit: check yesterday's ad spend against yesterday's KDP royalties. Roll it up weekly and monthly. The gap between the two answers almost every question you have about your ads. Everything else is texture.

The deeper point

The reason CPC is such a comfortable metric to obsess over is the same reason so much ads advice fixates on it. It gives you something to fiddle with. It updates every few hours. It lets you spend an evening tweaking headlines and feel productive.

But the ads exist to sell books. That's the whole job.

Get the numbers that measure the job in front of you (Attribution for the ad-level view, spend versus royalties for the truth) and put the vanity numbers off to one side where they belong.

You'll make calmer decisions. You'll spend less. And you'll almost always sell more.

That's it for this week. Thanks for reading. See you next Saturday.

To Your Success
– Matt