Apple's free iBooks Author is an easy way to get started in electronic textbook publishing. Just know there's a middleman standing between you and your adoring public: Apple. Read more about Apple's tricky software license agreement, which as InformationWeek
's Thomas Claburn points out, puts severe restrictions on authors' rights.
BYTE's Chris Spera has his own opinion about Apple's moves in the textbook market.
You can save your ebook as an Adobe Acrobat PDF file, but the PDF ebook won't preserve all your media. For instance, video files will not play from a PDF read in iBooks. Instead the user will see an image placeholder.