Amazon Ads sit directly inside the world's largest book marketplace, in front of readers who are already in purchase mode. That's a fundamentally different audience from Facebook or TikTok, where you're interrupting people who came for entertainment. When someone searches "dark romance enemies to lovers" on Amazon, they're shopping. That intent is why Amazon Ads can work so well — and why getting them wrong is so costly.

This guide covers Sponsored Products (the ad type that matters most for most authors) and Lockscreen ads, how targeting works, what bids to start with, and how to actually know if your campaigns are making money.

The Two Ad Types Authors Should Know

Sponsored Products

Sponsored Products are the ads you see in Amazon search results and on product detail pages — they look almost identical to organic results, with a small "Sponsored" label. When a reader searches for a book like yours, your book can appear above or between the organic listings. These are pay-per-click: you only pay when someone actually clicks on your ad.

Sponsored Products are the foundation of any Amazon ads strategy for authors. They're the most controllable, the easiest to optimize, and where the majority of successful authors focus their budget.

Lockscreen Ads

Lockscreen ads (sometimes still called Product Display Ads or Kindle Lockscreen Ads) appear on the lock screens of Kindle devices and in the Kindle app. They show your book cover with a short tagline to Kindle readers while their device is idle. These work best for visually striking covers and books in popular KU genres, since the audience is already Kindle-native. They're less beginner-friendly than Sponsored Products and harder to optimize — start with Sponsored Products first.

How Targeting Works

Amazon lets you target ads in two fundamentally different ways: by keyword (what people are searching for) and by ASIN (specific books or products on Amazon). Both have distinct uses.

Keyword Targeting

Keyword targeting shows your ad when someone searches for those words. Amazon offers three match types:

  • Broad match — Amazon shows your ad for searches that include your keyword in any order, plus variations. "Dark romance" broad might trigger on "dark romance enemies to lovers slow burn." High reach, lower relevance, can waste budget on irrelevant searches.
  • Phrase match — Your ad shows when the search includes your keyword as a phrase, in order, with possible words before or after. "Dark romance" phrase would match "best dark romance books 2025" but not "romance dark enemies."
  • Exact match — Your ad only shows when the search exactly matches your keyword (or very close to it). The most precise targeting. Usually higher conversion rates and the best data for optimization.
Campaign structure tip: Run exact match and broad match keywords in separate campaigns. This lets you see which match type is driving results and manage bids independently. Never mix match types in the same campaign — you lose the ability to interpret your data.

ASIN Targeting

ASIN targeting lets you place your ad directly on a competitor book's product page. When a reader is looking at a popular book in your genre, your book appears in the "Sponsored products related to this item" section below the main listing. This is one of the most powerful targeting strategies available — you're reaching readers who've already demonstrated interest in your genre at the exact moment they're deciding what to read next.

To find ASINs to target: go to Amazon, search for bestselling books in your genre and subgenre, and copy the ASINs from their product URLs (the B0XXXXXXXX string). Target 10–20 closely comparable titles in a dedicated ASIN campaign.

What Bids to Start With

Setting bids correctly from the start avoids two common mistakes: bidding so low your ads never serve, and bidding so high you burn budget before you have any data to work with.

For most fiction genres, start with bids of $0.25–$0.40 per click for keyword campaigns. For popular genres (romance, thriller) where competition is higher, you may need to go to $0.40–$0.55 to win impressions. For ASIN targeting campaigns, $0.20–$0.35 is often sufficient.

Amazon will show you suggested bids when you set up a campaign — treat these as a ceiling, not a floor. Start below the suggested bid and increase gradually once you have click data. Amazon's suggested bids are often inflated because they benefit from you spending more.

Set a daily budget of $5–$10 per campaign when you're starting out. This gives you enough daily data to analyze without overcommitting before you know which campaigns are working.

Understanding ACoS: Is Your Ad Actually Profitable?

ACoS stands for Advertising Cost of Sale, and it's the key metric for evaluating whether your Amazon ads are making money. The formula is simple:

ACoS = Ad Spend ÷ Ad Revenue × 100

If you spent $10 on ads and those ads generated $50 in book sales, your ACoS is 20%. But what's a good ACoS? That depends entirely on your royalty rate.

Calculating Your Break-Even ACoS

Break-even ACoS is the ACoS at which your ad spend exactly equals your royalty. Here's how to calculate it:

  • A $4.99 ebook on Amazon KDP at 70% royalty earns approximately $3.45 per sale
  • Break-even ACoS = (Royalty per sale ÷ List price) × 100
  • = ($3.45 ÷ $4.99) × 100 = 69%

This means any ACoS below 69% is technically profitable for that book. But "technically profitable" isn't the goal — you want a healthy margin. Target an ACoS of 30–50% for a single book. If you have a series, you can tolerate a higher ACoS (or even a loss) on book one, because you're buying readers who will purchase the rest of the series.

For a $2.99 ebook at 70% royalty ($2.09 per sale), break-even ACoS is about 70%. For a $9.99 ebook at 70% ($6.99 per sale), break-even is about 70% too — so the royalty rate matters more than the price at standard 70% territory.

Negative Keywords: Stop Wasting Money

Negative keywords tell Amazon not to show your ad for certain searches. They're one of the most important (and most neglected) parts of Amazon ads management.

Check your Search Term report weekly. Any search term that generated clicks without a sale after 5–10 clicks is a candidate for a negative keyword. Common patterns to negative out: genre terms that are too broad (just "romance" if you're writing a specific subgenre), competitor author names you've accidentally picked up, and terms with clearly wrong intent ("free romance books," "romance audiobook").

Adding negatives regularly is how you make a broad match campaign progressively more efficient without increasing bids.

When to Pause, When to Scale

Give new campaigns at least 2–3 weeks before making major decisions — Amazon needs time to find your audience and you need enough data to see patterns. But there are clear signals for both directions:

Pause when:

  • ACoS is above break-even after 30+ clicks and no sign of improving
  • Impressions are high, clicks are very low (under 0.1% CTR) — your cover or title isn't converting
  • A specific keyword is burning through budget with zero sales over 15+ clicks

Scale when:

  • ACoS is comfortably below break-even and the campaign has been stable for 2+ weeks
  • Raising daily budget produces proportional results (not just more ACoS)
  • Specific keywords are consistently profitable — raise bids on those keywords specifically

What Not to Do

A few mistakes that trip up almost every beginner:

  • Running only broad match keywords. Broad match will find you, but it will also waste your budget on irrelevant searches. Always have an exact match campaign alongside broad.
  • Adding hundreds of keywords at launch. More keywords isn't better — it spreads your budget too thin to get meaningful data on anything. Start with 20–30 tightly relevant keywords per campaign.
  • Not checking the Search Term report. Your actual search term data (what people searched before clicking your ad) is the most valuable information Amazon gives you. Check it weekly and mine it for new exact match keywords and negative keywords.
  • Turning campaigns off and on repeatedly. Amazon's algorithm needs consistency. Toggling campaigns off resets their learning. Let campaigns run and adjust bids instead.
  • Starting Amazon ads before you have reviews. Clicks to a book with zero reviews convert poorly. Get at least 5–10 reviews live before you spend a dollar on ads.
Remember: Amazon ads amplify what's already working. A book with a great cover, relevant keywords, and a compelling description will respond to ads. A book without those fundamentals will just lose money faster. Fix the organic listing before you pay to promote it.

Before you spend on ads, make sure your book can hold up to the readers you drive to it. A bad reading experience produces bad reviews, and bad reviews kill ad performance. Check our book launch strategy guide for the full pre-launch checklist, and consider getting professional editorial feedback on your manuscript before you start any paid promotion.