Advertising books on KDP

If you advertise books on KDP, everything above applies, with one big problem. The ACOS in your ads console only counts order sales. The console does show estimated page reads and royalties from Kindle+ (Kindle Unlimited until October 2026), but ACOS leaves them out, so a book that earns most of its money from page reads can show a terrible ACOS while making money.

That’s why authors get told to ignore ACOS and just compare royalties to ad spend. That’s too blunt to manage keywords with. You can fix the number instead.

Blended profit and blended ACOS

You can’t add order sales and page-read royalties together as they are. Royalties are money in your pocket. Order sales are the list price, and you only keep a share of that.

So first turn sales into profit with your average margin. Total royalties from orders divided by total list price of those orders gives you that margin.

Average margin × ad sales + estimated page-read royalties = blended profit

Ad spend ÷ blended profit = blended ACOS

Because margin is already taken out, break-even is 100%. A $100 spend that brings in $100 of blended profit pays for itself. Below 100% the ads make money, above it they cost money.

Page reads after the attribution window

Page reads only count toward your ads if they happen within 14 days of the click. A reader who borrows your book and starts it next month, or finishes it in week three, earns you royalties the console never credits to the ad.

Nobody can tell you exactly what share of reads happens in those 14 days. It depends on genre, length and how fast your readers binge. A romance audience might finish 80 to 90% within two weeks. A fantasy reader with a long backlog might only get 20 to 30% done. Pick a percentage you believe and lean conservative (higher).

Estimated royalties ÷ your 14-day read share = extended royalties

If half of reads happen in the window and the console shows $100 of royalties, that’s about $200. Use the extended number in blended profit.

Series read-through

Someone buys book one from your ad, likes it, and goes on to buy book two, three and four on their own. The ad gets credit for book one only.

Your series read-through rate fixes that. Divide book two’s orders (or page reads) by book one’s, book three’s by book two’s, and so on. If 80% of book one readers buy book two, then 100 ad orders of book one are worth about 80 more orders of book two, and some of those carry on to book three.

Add those up and you get your ad impact multipliers. If every ad order of book one leads to two more orders down the series, each ad order is really worth three, a 3x order multiplier. Page reads get their own multiplier the same way, and the extended-reads adjustment stacks on top.

None of this is exact. You can’t measure cross-series buys or how much organic ranking the ads bought you. But a reasonable estimate beats ignoring ACOS completely, and it tells you which keywords are actually earning their spend.