book-cover-design

SKILL.md

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
```bash
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

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