EPUB


Works on iPhone, iPod Touch, iPad, Sony Reader, Kobo Reader, the Nook (Barns and Noble) and Android phones; NOT KINDLE


AZW


Works on iPhone, Android phones, BlackBerry, computers (Mac and PCs), iPad, Android tablets and Windows 8 tablets.


PDF


Works on computers (Mac and PCs); not recommended for smartphones.


MOBI


Works on MobiPocket’s reading software (available for many PDAs and smartphones), can be used by third-party readers such as Stanza, FBReader, Kindle (for Mac and PCs) and STDU Viewer.