The TrustACOS Blog
Real Amazon Ads profitability for Kindle Unlimited and series authors. The numbers Amazon’s ACOS leaves out, and what to do about them.
June 16, 2026
Break-Even ACOS for a Series Is Not 70%. It Might Be 400%.
The 'keep ACOS under 70%' rule is for standalone books. If you write a series, your real break-even ACOS can be 300% or higher. Here is how to calculate yours.
Read moreJune 16, 2026
What Is a Kindle Unlimited Read Actually Worth? (KENP Math for Ad Decisions)
You cannot judge Amazon Ads profitability in KU without knowing what a borrow is worth. Here is the KENP math, a worked per-borrow value, and how to use it in your ACOS.
Read moreJune 16, 2026
Why Authors Lose Money on Amazon Ads (and How to Tell If You Are)
Most authors who think they are losing money on Amazon Ads are making one of two very different mistakes. Here is how to tell which one is yours, and what to do about each.
Read moreJune 15, 2026
Your Amazon ACOS Is Lying to You (If Your Books Are in Kindle Unlimited)
Amazon's ACOS ignores KENP page reads and series read-through, so it quietly mislabels profitable campaigns as losers. Here is the real math, with a worked example.
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