Install the belt CLI skill: npx skills add belt-sh/cli

Book Cover Design

Create genre-appropriate book covers with AI image generation via inference.sh CLI.

Quick Start

Requires inference.sh CLI (belt). Install instructions

belt login

Generate a thriller cover concept

belt app run falai/flux-dev-lora --input '{

"prompt": "dark moody book cover art, lone figure standing at end of a rain-soaked alley, dramatic chiaroscuro lighting, noir atmosphere, cinematic, high contrast shadows",

"width": 832,

"height": 1248

}'

## Genre Conventions

Readers judge books by covers. Matching genre expectations is critical — a romance reader will skip a cover that looks like sci-fi, regardless of content.

### Fiction

| Genre | Palette | Imagery | Typography | Mood |

|-------|---------|---------|------------|------|

| **Thriller/Mystery** | Dark (black, navy, blood red) | Lone figure, urban scenes, shadows | Bold sans-serif, all caps | Tense, ominous |

| **Romance** | Warm (pink, red, gold, soft purple) | Couples, flowers, scenic backdrops | Script/cursive, elegant serif | Passionate, dreamy |

| **Sci-Fi** | Cool (blue, teal, purple, silver) | Space, tech, geometric shapes | Clean sans-serif, futuristic | Vast, technological |

| **Fantasy** | Rich saturated (emerald, crimson, gold) | Swords, magic, landscapes, creatures | Decorative serif, ornamental | Epic, magical |

| **Literary Fiction** | Muted, sophisticated | Abstract, minimal, symbolic | Elegant serif, understated | Thoughtful, artistic |

| **Horror** | Dark with high contrast pops | Faces, shadows, isolation, decay | Distressed, bold, dripping | Dread, unease |

| **Historical** | Sepia, muted period-accurate | Period clothing, architecture, artifacts | Classical serif | Nostalgic, authentic |

### Non-Fiction

| Category | Style | Imagery | Typography |

|----------|-------|---------|------------|

| **Business/Self-help** | Clean, bold, 2-3 colors | Minimal or none, icon optional | Large bold sans-serif title |

| **Memoir** | Personal, warm | Author photo or atmospheric scene | Mix of serif and sans |

| **Science/Academic** | Professional, structured | Diagrams, abstract visuals | Clean serif, structured layout |

| **Cookbook** | Appetizing, bright | Hero food photograph | Warm, inviting fonts |

| **Travel** | Vibrant, aspirational | Destination photography | Adventure-style fonts |

## Cover Sizing

### Print (Trim Sizes)

| Format | Dimensions | Common For |

|--------|-----------|------------|

| Mass market paperback | 4.25 x 6.87" | Genre fiction |

| Trade paperback | 5.5 x 8.5" | Most fiction/non-fiction |

| Standard | 6 x 9" | Non-fiction, textbooks |

| Large format | 7 x 10" | Coffee table, art books |

### Digital

| Platform | Cover Size | Aspect Ratio |

|----------|-----------|--------------|

| Amazon Kindle | 2560 x 1600 px (min 1000 x 625) | 1.6:1 |

| Apple Books | 1400 x 1873 px minimum | ~3:4 |

| General ebook | 2500 x 3750 px | 2:3 |

### Spine Width

Approximate: **page count / 400 = spine width in inches** (varies by paper stock).

- 200 pages ≈ 0.5" spine

- 400 pages ≈ 1.0" spine

## Layout Zones

┌─────────────────────────┐

│ TITLE ZONE │ ← Top 1/3: Title must be readable here

│ (largest text) │ This is what shows in thumbnails

│ │

│ │

│ MAIN IMAGE │ ← Middle: Core visual/illustration

│ ZONE │ The emotional hook

│ │

│ │

│ SUBTITLE / │ ← Bottom area: Author name, subtitle

│ AUTHOR ZONE │ Smaller text, less critical at thumbnail

└─────────────────────────┘

## The Thumbnail Test

Your cover will be seen at **80x120px** on Amazon, 60x90px in search results, and ~40x60px on mobile grids.

**At thumbnail size, readers must be able to identify:**

1. The genre (from color and composition)

2. The title (if large enough)

3. The mood (from imagery)

**Test:** shrink your cover to 80px wide. If you can't read the title or identify the genre, redesign.

## Prompting by Genre

### Thriller

belt app run falai/flux-dev-lora --input '{

"prompt": "dark cinematic book cover scene, silhouette of a person standing before a foggy bridge at night, single streetlamp casting long shadows, noir atmosphere, high contrast, desaturated blue tint, dramatic tension",

"width": 832,

"height": 1248

}'

### Romance

belt app run bytedance/seedream-4-5 --input '{

"prompt": "romantic soft-focus scene, couple silhouetted against golden sunset on a beach, warm pink and gold tones, bokeh lights, dreamy atmosphere, soft pastel sky, intimate mood",

"size": "2K"

}'

### Sci-Fi

belt app run falai/flux-dev-lora --input '{

"prompt": "science fiction book cover art, massive space station orbiting a ringed planet, deep blue and teal color palette, stars and nebula background, hard sci-fi aesthetic, cinematic scale, clean geometric architecture",

"width": 832,

"height": 1248

}'

### Fantasy

belt app run xai/grok-imagine-image-pro --input '{

"prompt": "epic fantasy book cover illustration, ancient stone castle on a cliff overlooking a misty valley, magical aurora in the sky, rich emerald and gold colors, detailed environment, sense of wonder and adventure",

"aspect_ratio": "2:3"

}'

### Non-Fiction / Business

belt app run falai/flux-dev-lora --input '{

"prompt": "minimal abstract book cover background, clean gradient from deep navy to white, subtle geometric pattern, professional and modern, negative space, corporate aesthetic",

"width": 832,

"height": 1248

}'

## Typography Rules

**AI cannot render text reliably.** Generate the cover art/background with AI, then add typography in a design tool.

### Title Hierarchy

- **Title** — largest, most prominent, top 1/3 of cover

- **Subtitle** — smaller, below title or at bottom

- **Author name** — bottom of cover, size depends on author recognition

### Font Pairing by Genre

- Thriller: bold sans-serif title + condensed sans-serif author

- Romance: script/cursive title + elegant serif author

- Sci-Fi: geometric sans-serif for both

- Fantasy: decorative/medieval serif title + clean serif author

- Business: heavy bold sans-serif title + light sans-serif subtitle

## Iteration Workflow

1. Generate 5+ concepts across different models

belt app run falai/flux-dev-lora --input '{"prompt": "...", "width": 832, "height": 1248}' --no-wait

belt app run bytedance/seedream-4-5 --input '{"prompt": "..."}' --no-wait

belt app run xai/grok-imagine-image-pro --input '{"prompt": "...", "aspect_ratio": "2:3"}' --no-wait

2. Refine best concept with image-to-image editing

belt app run bytedance/seededit-3-0-i2i --input '{

"prompt": "make the sky more dramatic with storm clouds, increase contrast",

"image": "path/to/best-concept.png"

}'

3. Upscale for print quality

belt app run falai/topaz-image-upscaler --input '{

"image": "path/to/final-cover.png",

"scale": 4

}'

## Common Mistakes

Mistake
Problem
Fix

Wrong genre signals
Readers skip it
Study bestsellers in your genre

Title too small
Invisible at thumbnail
Title should fill top 1/3

Too much detail
Muddy at small sizes
Simplify, use negative space

AI-generated text
Garbled letters
Add text in design tool

Centered everything
Static, boring
Use asymmetry intentionally

Following trends blindly
Dates quickly
Classic genre conventions endure

## Checklist

-  Genre instantly recognizable from colors and composition

-  Title readable at 80px wide (thumbnail test)

-  No AI-generated text on cover

-  Works in both color and greyscale

-  Correct dimensions for target platform

-  Author name visible but not competing with title

-  High resolution (300 DPI for print, 2500px+ for digital)

-  Spine text readable (for print)

## Related Skills

npx skills add inference-sh/skills@ai-image-generation

npx skills add inference-sh/skills@prompt-engineering

npx skills add inference-sh/skills@image-upscaling