Book Cover Design

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

Non-Fiction

Cover Sizing

Print (Trim Sizes)

Digital

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

1. Title — largest, most prominent, top 1/3 of cover
2. Subtitle — smaller, below title or at bottom
3. 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",
  "upscale_factor": 4
}'

Common Mistakes

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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