eBook Formatting Best Practices
get it right the first time
A poorly formatted ebook is one of the fastest ways to earn a one-star review. Readers notice when chapter headings are inconsistent, when images overflow off screen, or when the table of contents links to the wrong page. The good news is that professional-quality formatting does not require expensive software or a design degree. It requires attention to a handful of fundamentals that most indie authors overlook. Whether you are formatting in Vellum, Sigil, Calibre, or exporting from Scrivener, these principles apply across every tool.
Clean CSS and Semantic HTML
The single biggest formatting mistake is inline styling. When you copy and paste from Microsoft Word into an EPUB editor, you bring along hundreds of hidden style declarations: specific font sizes, hardcoded margins, color values, and line-height overrides. These look fine on your laptop but break horribly on a Kindle Paperwhite or a Kobo Libra. Instead, use a clean external stylesheet with relative units like em and percentages. Define your body text, headings, blockquotes, and lists as simple CSS classes, and let the reading device handle the rest. Strip out every inline style you can find. Your ebook should be semantic HTML with a light stylesheet, not a Word document crammed into an EPUB container.
Table of Contents and Navigation
Every EPUB needs two types of table of contents: the inline HTML TOC that readers see as a page in the book, and the NCX or navigation document that powers the device menu. Both must be present and both must work. Apple Books will reject your upload if the navigation document is missing or malformed. Link every TOC entry to the correct anchor in your chapter files, and test every link on at least two different reading apps before you publish. A broken TOC is the number-one reason books get rejected by retailers.
Image Handling
Images in ebooks need to be optimized for screens, not print. Use JPEG for photographs and PNG for graphics with transparency or sharp lines. Keep file sizes under 800KB per image and total EPUB size under 20MB to avoid upload issues with certain retailers. Always set width to 100% with a max-width in your CSS so images scale gracefully across phone screens and tablets. Include alt text for accessibility. And never, ever rely on images for text content. If your chapter title is an image, screen readers cannot read it, search cannot index it, and your book fails accessibility requirements on every major platform.