In flowing books, supplying landmarks in the navigation document is recommended but not required.
In flowing books, divide each chapter into its own XHTML document. Apple Books creates a page break between documents.
Separating chapters into documents improves performance in Apple Books.
Use header tags (for example, <h1>, <h2>) for headers. Do not create a header using <p> styled to look like a header. Apple Books relies on HTML semantics when laying out the text of a book. Using a <p> instead of a header results in poor text layout such as unexpected hyphenation.