EPUB is a publication package
An EPUB is more than a text file with an .epub extension. Under the hood it is a structured package containing XHTML content documents, CSS, navigation, metadata, images and other resources. That structure allows reading systems to understand what the publication contains and how readers should move through it.
Why reflowable EPUB is different from PDF
A PDF preserves page geometry. A reflowable EPUB preserves structure and lets the reading system adapt presentation to the screen and the reader’s settings. That is why normal trade ebooks should not be designed around fixed page numbers, exact line breaks, or print-only spacing.
What a professional EPUB should contain
- Clear document hierarchy
- Working navigation
- Consistent styles
- Accurate publication metadata
- Correctly referenced images and resources
- Language information
- Validation against the EPUB specification
What authors should do before conversion
Finish substantive editing first. Use consistent chapter headings, provide the final cover and identifiers, identify images that need alternative text, and decide where the book will be distributed. Production is smoother when those decisions are stable before conversion begins.
Primary sources
- W3C EPUB 3.3 — the EPUB 3.3 Recommendation
- W3C EPUB overview — W3C overview of EPUB 3.3