Prompts for Book Covers

The first mistake almost everyone makes is prompting for a scene from the book. A cover is not a scene. It is a signal that tells a browsing reader what kind of experience is inside, delivered in about a second and a half at the size of a postage stamp. Prompt for the signal, not the plot.

That reframing changes what you write. Instead of “a detective standing over a body in a rain-soaked alley at night”, you get further with “a single wet streetlight, deep shadow, muted teal and amber, empty frame”. The second one is not a worse description of the book. It is a better description of a cover, because it has one idea in it and that idea survives being shrunk.

One Object, Lots of Empty Space

Working covers are overwhelmingly built on a single dominant element against a simple ground: one figure, one object, one shape. Ask for that explicitly. Say the subject is centred or offset, say the background is flat or plainly textured, and say where the emptiness is — “upper third empty”, “wide clear area above the subject”. You need that space, because the title and your name are going into it later in a design tool, not into the generated image.

Leaving the room is the part people forget. A gorgeous edge-to-edge composition is unusable the moment you have to lay type over it, and cropping to make space usually destroys the balance that made it good. Decide on the type area before you generate, and prompt for it as part of the picture.

Genre Lives in Palette and Medium

Readers recognise genre faster than they read anything, and they recognise it from colour and finish. Literary fiction runs to restraint: paper texture, hand-drawn or painted marks, two or three colours. Thrillers run to high contrast, hard shadow, saturated single accents. Fantasy carries ornament and depth. Romance runs warm, bright and often illustrated in flat vector shapes.

Those are conventions, and the practical move is to name the convention rather than describe it in adjectives. “1960s Penguin paperback design”, “modern flat vector illustration, three colours”, “gouache painting on cold-press paper” each pull an entire visual tradition into the frame. That is more reliable than stacking words like moody or dramatic, which drift.

Test It Small Before You Judge It

Generate at full size, then look at the result scaled down to about two hundred pixels tall — the size it will actually appear in a store listing. Most covers fail here rather than at full resolution. Fine detail turns to noise, low-contrast subjects dissolve into their background, and a composition with three competing focal points becomes a smudge.

If it fails small, the fix is usually subtraction: fewer elements, more contrast between subject and ground, larger shapes. Rewrite the prompt to remove a thing rather than to add clarity, and check again at thumbnail size. Covers that survive that test tend to be simpler than the ones you wanted to make.