Read Aloud Books: SMIL Files Clarification
When adding a SMIL file to a read aloud book, make sure you specify the correct media-type for your audio files in the OPF (the expected media-type for m4a files is "audio/m4a"). If the media-type is incorrect, the audio will not play after customers have purchased the book. This issue will not be evident when testing locally prior to delivering to iBooks. See Adding a SMIL File and Audio File to an EPUB.
Fixed-Layout Books: Layout Clarification
When creating fixed-layout books in EPUB 3, you must include the following prefix attribute in the <package> element in the OPF file:
<package xmlns="http://www.idpf.org/2007/opf" unique-identifier="bookid" version="3.0" prefix="rendition: http://www.idpf.org/vocab/rendition/#"> See Defining Book Layout Metadata for more information.
Fixed-Layout Books: Text Positioning
When using absolute positioning to place text in fixed-layout books, Apple recommends positioning the text at the sentence or paragraph levels; not at the word level. Positioning at the word level results in a poor user experience when selecting text and using search. See Text for more information.
Marketing Screenshots
You can deliver screenshots for iPad Pro 12.9-Inch Retina Displays. Below lists the sizes in pixels shown width by height.
2048 x 2732: (iPad Pro portrait)
2732 x 2048: (iPad Pro landscape)