iBooks Author: supported file formats
You can add these kinds of digital files to an iBooks Author document:
Image files: JPEG, PNG, GIF, TIF, AI, BMP, PICT, PSD, and more
Note: The recommended file format is JPEG. If the image includes transparency, PNG is recommended. When the book is exported, all the images are optimized and stored as either JPEG or PNG files.
Video and audio files: MPV, M4A
Note: For the Media widget, you can add a video file or an audio file (in a format QuickTime supports) to your book. You can convert other types of files using iMovie, QuickTime Player, or Compressor. For the HTML widget, the suggested file formats are MP4 video files and M4A audio files. Any movie or audio file you add automatically becomes a widget in the book.
Document files: PDF