🎨 Elegant CSS Themes for the Calibre Viewer

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Transform your Calibre reading experience! ✨

This repository contains a unified CSS stylesheet offering three aesthetic and elegant themes for the Calibre E-book Viewer. Designed to be visually pleasing, modern, and highly readable, especially on high-resolution monitors.

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✨ Key Features

• 🌓 Automatic Dual Mode: Seamlessly adapts to Calibre's light and dark color schemes without code changes.
• 🎨 Three Carefully Crafted Themes: Choose from "Modern Classic," "Professional Elegance," or "Warm Minimalist" to match your mood.
• offline: Local Fonts: Utilizes fonts installed on your system for fast performance and no internet dependency.
• 👓 Readability Focused: Optimized typography and spacing to reduce eye strain during long reading sessions.
• 🔧 Easy to Customize: Switch between themes or tweak colors to your liking by editing a few lines.

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📸 Preview

Here you can place a screenshot showcasing how the themes look in your Calibre. A picture is worth a thousand words! (The variations in fonts and style, not colors, are very subtle to perceive)

Night 🌓 (Theme 1: Modern Classic)

Night 🌓 (Theme 2: Professional Elegance)

Night 🌓 (Theme 3: Warm Minimalist)

Day ☀️ (Theme 1: Modern Classic)

Day ☀️ (Theme 2: Professional Elegance)

Day ☀️ (Theme 3: Warm Minimalist)

Visual Comparison

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🖋️ Requirements

For the themes to work correctly, you need to have Calibre installed and the following font families on your operating system. All are free and open-source.

Theme 1: Modern Classic

• Literata (Google Fonts)
• Inter (Google Fonts)

Theme 2: Professional Elegance

• Spectral (Google Fonts)
• IBM Plex Sans (Google Fonts)

Theme 3: Warm Minimalist

• Alegreya (Google Fonts)
• Lato (Google Fonts)

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🚀 How to Use

Option 1 (Easy)

1. Install the fonts for at least the theme you wish to use (though installing all is recommended).
2. Download the calibre-viewer-theme-number-1 file from this repository, choosing based on the theme you like.
   • number-1 for Theme 1: Modern Classic
   • number-2 for Theme 2: Professional Elegance
   • number-3 for Theme 3: Warm Minimalist
3. Open any book in the Calibre E-book Viewer.
4. Click on the Preferences icon (⚙️ or a hammer).
5. Go to the Styles tab.
6. Copy and paste the entire content of the file. Click Apply, and you're done! Reload the book and enjoy!

Option 2 (Manual)

1. Install the fonts for at least the theme you wish to use (though installing all is recommended).
2. Download the calibre-viewer-themes-all-in-one.css file from this repository.
3. Open any book in the Calibre E-book Viewer.
4. Click on the Preferences icon (⚙️ or a hammer).
5. Go to the Styles tab.
6. Copy and paste the entire content of the calibre-viewer-themes-all-in-one.css file into the text box.
7. Activate your preferred theme. At the end of the code, you'll find a section called /* --- FONT APPLICATION BY THEME --- */. To activate a theme, simply "uncomment" it (remove the /* and */ symbols surrounding it).

Important! Ensure only one theme is active (uncommented) at a time.

For example, to activate Theme 2:

Before:

/* THEME 2: PROFESSIONAL ELEGANCE */
/*
body { font-family: var(--font-body-elegante); }
h1, h2, h3, h4, h5, h6 { font-family: var(--font-headings-elegante); }
*/

After:

/* THEME 2: PROFESSIONAL ELEGANCE */

body { font-family: var(--font-body-elegante); }
h1, h2, h3, h4, h5, h6 { font-family: var(--font-headings-elegante); }

Click Apply, and you're done! Reload the book and enjoy!

🔧 Customization Changing Themes (Manual)

You can switch themes at any time by following step 7 above. Remember to comment out the old theme before uncommenting the new one.

Adjusting Colors

All colors are defined as CSS variables at the beginning of the file, in the :root section. Feel free to modify the rgb() values to create your perfect palette.

:root {
    /* Light Color Palette */
    --bg-light: rgb(245, 241, 233);
    --text-light: rgb(40, 40, 40);
    
    /* Dark Color Palette */
    --bg-dark: rgb(25, 25, 30);
    --text-dark: rgb(220, 215, 205);
}

🖥️ Recommended Font Size

These themes particularly shine with a slightly larger font size than the Calibre viewer's default.

A good starting point on a large monitor (like a 24") is between 20 and 22pt. You can adjust this in (I suggest changing it from Calibre itself and not from the code, within the open book, right-click, Font Size, and increase the amount there)

✍️ Credits

Design and Creation: Gemini 2.5 Pro