An ebook cover has one job, performed at one size: convince a scrolling stranger, at the size of a postage stamp, that this book is for them. Everything else about cover design is decoration on that fact. This guide covers what actually converts, the specs Amazon enforces, where AI cover generation genuinely helps, and the four mistakes that mark a book as amateur from across the room.
The thumbnail test is the whole exam
On Amazon, in a Gumroad grid, in a social feed, your cover is 80 to 150 pixels wide when the buying decision starts. Shrink any cover you are considering to that size and ask three questions: can I read the title, can I tell the genre, does anything pull the eye. If the answer to all three is yes at stamp size, the cover works everywhere bigger. Most covers fail the first question alone, and no full-size beauty rescues a failed thumbnail.
What converts, in order of weight
- Genre signal. Every shelf has a visual dialect: soft illustration and hand lettering for cozy fiction, bold type on flat color for business, dark tones and serif gravity for thrillers. Buyers read the dialect before the title. Matching it is not conformity; it is telling the right readers this is for them.
- Title legibility. Big type, high contrast, two fonts maximum. The title takes a third of the cover or more for nonfiction. Thin elegant scripts die at thumbnail size, always.
- One focal image. One object, one figure, one strong shape. Scenes with five elements become mud at small sizes. The strongest covers are almost embarrassingly simple.
- The subtitle, working. For nonfiction the subtitle carries the promise: who this is for and what changes. It can be small on the cover as long as it is readable on the product page.
Amazon's cover specs, in one table
| Property | Requirement |
|---|---|
| Recommended size | 2,560 x 1,600 pixels, ratio 1.6:1 |
| Minimum size | 1,000 pixels on the longest side |
| Format | JPEG or TIFF for the ebook cover |
| Color | RGB for ebooks; print covers are a separate CMYK world |
| Content | No prices, no URLs, nothing that contradicts the listing |
AI cover generation, honestly
Image models are now genuinely good at cover art, and genuinely bad at cover typography. The failure you have seen everywhere: warped letters, almost-words, titles baked into the artwork at the wrong size. The workable division of labor is the one professional designers always used: generated or photographed art underneath, real typography set on top as live text. That is how Bookbind builds covers: the artwork is generated to your chosen direction, and the title, subtitle and your author name are set as actual type, so letters are letters and your name is spelled like your name. An AI-generated cover also needs the KDP disclosure ticked at upload; the rules are in our disclosure guide.
The four amateur tells
- Word soup. Title, subtitle, tagline, series name, review quote, author name. Something has to go, and it is usually the tagline.
- Thin fonts on busy art. If the type needs an outline to be readable, the background is wrong, not the type.
- Wrong-shelf signals. A literary cover on a how-to book loses both audiences at once.
- Full-size thinking. Designed on a big monitor, judged on a big monitor, dead at thumbnail. Judge small first.
A cover is also downstream of knowing exactly who the book is for, which is decided when the book is planned. That thread runs through our guide to writing an ebook with AI: a book with a named reader almost designs its own cover.
See title options and cover directions proposed for one idea, and pick the pair that sells it.
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