Text Direction: Tatechuyoko
In vertical text, it is sometimes preferable to include a short run of horizontal numbers or Latin text. This is known as Tatechuyoko. To create Tatechuyoko, you must use the CSS property, -webkit-text-combine. See Text Directions for details.
Text Direction: Clarification
Each content document can support a single writing-mode value. If you want both horizontal and vertical text in your book, then each text direction must be split into separate content documents. Tatechuyoko should not be created using the CSS writing-mode property.
Gaiji Images
To make a gaiji image accessible for readers who use VoiceOver, the alt attribute for a gaiji image must be included. See Interior Image Requirements for details.
Book Cover/Marketing Image
The 2 million pixel limit on image size does not apply to the external cover/marketing image that is sent alongside the book asset. It applies only to images inside the book asset.
Book Versioning
Apple recommends that you declare the first asset delivered to iBooks version 1.0. The version number is consumer-facing and is meant to manage delivering updates to consumers. Future versions should increment as is appropriate.
Changed the word “preview” to “sample.” Added a sentence to explain where the What’s New text is displayed.
Fonts
iBooks' fonts follow the font orientation guidelines of UTR (Unicode Technical Report) 50 draft 6.
Flowing Books: Scrolling with Vertical Text
For flowing books, iBooks has several viewing themes that the reader can select. The Scroll theme scrolls vertically for books with horizontal text, and scrolls horizontally for books with vertical text. This is useful for a book with vertical Japanese or Chinese text. When rendered with iBooks' Scroll theme, vertical text is most easily read scrolling right to left on the horizontal axis. See Scrolling in Flowing Books for details on scrolling, and the metadata required for defining a book's scroll direction.
Fixed-Layout Books: Hide Book Binding
If you create a fixed-layout book that is two documents per spread, but you do not want it to have the book-like appearance, you can hide the book binding by including the binding layout property and giving it a value of false. See Defining Book Layout Metadata.
Fixed-Layout Books: Clarification
Nonlinear documents are not supported fixed-layout books; only flowing books support nonlinear documents.
Read Aloud Books: Clarification
If you include the readaloud attribute, you must also include the iBooks namespace and prefix in <html>. See Embedding Read Aloud Controls for an example.