High-quality eBook conversion is not a one-click export. It is a controlled production process that turns an edited source file into a semantically structured, accessible, validated, and device-tested publication. The safest default for most books is a reflowable EPUB. It allows readers to change text size, font, line spacing, margins, and device orientation. Fixed-layout EPUB should be reserved for content whose meaning depends on precise page composition. PDF may be appropriate for direct downloads or print-like reference material, but it is usually not the best primary retail eBook experience on small screens.
A reliable workflow has ten gates: define the edition and target stores; audit the source; normalize styles and structure; prepare images and special content; build the EPUB; add navigation, metadata, and accessibility; validate the package; inspect it visually on representative devices; preview it through retailer tools; then resolve defects and archive an approved master.
A high-quality eBook preserves the author’s meaning while adapting the presentation to reader-controlled screens. It should be:
Do not define quality as “it looks exactly like the printed page.” A reflowable eBook is not a miniature print PDF. The reader may enlarge the type, rotate the device, choose a different font, enable dark mode, or use a screen reader. The conversion must protect hierarchy, sequence, meaning, and usability when the surface changes.
Begin with a conversion specification. Record the title, subtitle, author and contributor names, language, publisher or imprint, publication date, rights, ISBN or platform identifier, source-file version, target stores, delivery deadline, and responsible approver.
Then classify the content. A novel with a few ornaments has different requirements from a mathematics textbook, cookbook, children’s picture book, graphic novel, workbook, or illustrated art book. Count chapters, images, tables, notes, equations, sidebars, languages, scripts, hyperlinks, audio or video, indexes, and any content that depends on page position.
Conversion begins after editorial approval. Correcting hundreds of typos after the EPUB is built creates avoidable cost and version risk. Freeze the manuscript, assign a version, and identify the authoritative file.
|
Source check |
Pass condition |
Typical defect |
| Editorial status | Words and order are approved | Tracked changes or late edits |
| Styles | Meaning uses consistent named styles | Manual font, tabs, and spaces |
| Hierarchy | Headings and chapters are logical | Visual headings without structure |
| Images | Original assets and rights are available | Low-resolution pasted graphics |
| Special content | Tables, notes, equations, and languages are logged | Converter must guess intent |
| Navigation | TOC matches actual content | Missing or wrong chapter labels |
| Metadata | Edition fields agree | Title or contributor variants |
| Source integrity | No hidden text, duplicate content, or placeholders | PDF extraction or OCR damage |
Use paragraph and character styles instead of visual tricks. A heading should be marked as a heading, not created by making body text larger and bold. A block quotation, caption, list, footnote, and scene break should each have a consistent semantic treatment.
A typical reflowable chapter uses a heading hierarchy, paragraphs, lists, block quotations, figures, captions, and notes. The HTML should express meaning before CSS supplies appearance.
Example structure:
Keep original source assets separate from the EPUB derivatives. Record the source filename, derivative filename, purpose, dimensions, color profile, compression, caption, alt text, and rights status.
Use a supported web image format appropriate to the content. JPEG is efficient for photographs. PNG is useful for line art, transparency, or graphics that degrade under photographic compression. SVG can be effective for scalable diagrams when target support and accessibility are managed. Do not convert every image blindly to one format.
Simple tables can remain real HTML tables with header cells and a logical reading order. Large or wide tables often fail on phones. Consider splitting them, simplifying columns, rotating the information model, or providing an accessible narrative alternative.
Never convert a data table to a flat image solely to preserve print appearance. That makes text difficult to enlarge or search and can block screen-reader access. If a visual table must be included, add an accessible equivalent.
Use a format supported by the target ecosystem, such as MathML where appropriate, plus careful fallback and accessibility treatment. An equation image needs meaningful text support. Test reading order, pronunciation, and display at different sizes.
Every note reference should link to the note; the note should provide a return path. Keep reference labels consistent. Test keyboard and screen-reader behavior as well as visual tapping.
Preserve meaningful spacing without locking ordinary text. Poetry may use line groups and intentional breaks. Code may require a preformatted treatment, horizontal overflow safeguards, and adequate contrast. Right-to-left or mixed-direction languages require correct language and direction metadata, not manual alignment.
A professional EPUB contains more than chapter files. It includes package metadata, a manifest of resources, reading order, navigation, styles, fonts if licensed and required, images, and the container structure.
Use a current EPUB standard appropriate to the delivery ecosystem. Prefer semantic HTML and restrained CSS. The reading experience should survive when a retailer modifies or overrides styles.
System or reader fonts are the most robust default for body text. Embed fonts only when licensing permits and the design need is real. Subset and obfuscate them according to the applicable specification and platform requirements. Test fallback behavior. A missing decorative font must not destroy hierarchy or replace characters with boxes.
Split files at sensible boundaries. Extremely large documents can load slowly, while excessive fragmentation complicates navigation. Each chapter file should declare language, follow the heading hierarchy, and include only required resources.
Provide an EPUB navigation document with accurate labels and destinations. Include landmarks such as cover, table of contents, and body matter when appropriate. If a legacy navigation structure is required by a channel or reading system, generate and test it without letting it conflict with the primary navigation.
The package metadata should agree with the retailer submission: title, contributors, language, identifier, publisher, date, rights, and accessibility metadata. Keep the display title separate from unsupported keyword tactics. Metadata quality means accuracy and consistency, not stuffing.
At minimum:
The Web Content Accessibility Guidelines inform many principles, while EPUB Accessibility defines publication-specific discovery and conformance practices. The European Accessibility Act and other laws may affect commercial eBooks in relevant markets. Legal obligations depend on the publisher, product, market, and date, so obtain qualified advice when compliance matters.
Good alt text is contextual. “Image” is useless. “Graph” is incomplete. For a decorative flourish, no spoken description may be needed. For a chart, communicate the conclusion and provide the underlying detail elsewhere when necessary. For a book cover, the title and author may be the meaningful content. Do not repeat a caption word for word unless it is genuinely the best equivalent.
Automated validation catches structural problems that visual review may miss. Run EPUBCheck on the unencrypted EPUB master. Record the validator version and archive the report.
Treat errors as release blockers unless an expert documents why a message is not applicable. Review warnings rather than dismissing all of them. A validator can flag missing resources, malformed markup, invalid metadata, duplicate IDs, broken references, unsupported properties, or package problems.
Use a representative device matrix rather than trying to own every device. Cover multiple rendering engines, screen sizes, operating systems, orientations, and accessibility settings.
|
Test environment |
Purpose |
Settings |
| Phone app | Small-screen stress | Portrait, landscape, large text |
| Tablet app | Medium and wide view | Themes and orientation |
| Dedicated eReader | E-ink reader experience | Fonts, margins, dark mode if supported |
| Desktop reader | Keyboard and large viewport | Resize window |
| Kindle Previewer | Retailer transformation preview | Representative device modes |
| Apple Books | Apple reading engine | Text size and themes |
| Kobo environment | Kobo rendering | Narrow screen and enlarged text |
| Assistive test | Reading order and semantics | Keyboard and screen reader sample |
Test at normal and enlarged text sizes. Change fonts, margins, line spacing, themes, and orientation. Check both light and dark modes. Use a phone-sized screen, a tablet-sized screen, and at least one dedicated eReader or faithful preview path when the audience uses them.
The approved EPUB master is the source of truth, but retailers may transform it. Preview the file through each intended retailer’s current tool or submission workflow.
Before: A chapter title is centered with spaces, followed by eight blank paragraphs to force the body onto a new screen.
After: The title uses a semantic chapter-heading style, the chapter begins at a controlled file or CSS boundary, and redundant empty paragraphs are removed.
After: The text links to the named section or note. A page list is included only when the edition has a legitimate print-correspondence need.
For most text-led retail books, a reflowable EPUB is the best master because it adapts to screens and reader preferences. Fixed-layout EPUB is suitable when precise composition is essential and supported. PDF is useful for some direct-download or page-faithful purposes but is not a universal replacement for EPUB.
A MOBI-first workflow is outdated. Current Kindle publishing workflows accept EPUB uploads and convert them for Kindle delivery. Follow the current Kindle Publishing Guidelines and test the EPUB in Kindle Previewer.
Software can extract content from a PDF, but the result often needs substantial reconstruction. PDFs can lose semantic structure, reading order, styles, links, notes, and correct text encoding. Budget for cleanup, proofreading, and accessibility instead of assuming an automatic export is production-ready.
EPUBCheck is the widely used open-source conformance checker for EPUB publications. It identifies many package, markup, metadata, and resource problems. Passing EPUBCheck is necessary for a professional workflow but does not replace visual, editorial, functional, accessibility, or retailer testing.
Test representative rendering engines and use cases rather than an arbitrary device count. Include a phone, tablet, dedicated eReader or faithful preview path when relevant, and the current retailer preview tools for target stores. Test large text, orientation, light/dark themes, and assistive use.
Use the current EPUBCheck release to check conformance. The official download is version 5.4.0 as of October 21, 2026. A passing report does not prove visual or editorial quality.
Ace by DAISY adds automated accessibility checks. Human review still needs to confirm reading order, useful image descriptions and whether tables and notes communicate their meaning.
For Kindle, KDP’s accepted-file guidance supports EPUB, DOCX and KPF for relevant workflows. MOBI upload support has ended. Inspect the processed Kindle preview, not only the original EPUB.
Approve the release only when the source comparison, navigation, text resizing, images, notes, language, metadata and required accessibility checks pass. Archive the approved EPUB, source files and QA reports together.
For related preparation work, use the manuscript preparation checklist. For production help, agree on deliverables and tests with an eBook conversion service.
