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

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

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",
  "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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