What are some alternatives?
Amazon Kindle - Amazon Kindle software lets you read ebooks on your Kindle, iPhone, iPad, PC, Mac, BlackBerry, and...
Sigil - Sigil is a multi-platform WYSIWYG ebook editor. It is designed to edit books in ePub format.
FBReader - FBReader is an e-book reader for various platforms. Features:
calibre - Ebook manager, viewer & converter
Wondershare MePub - A Simple yet Powerful EPUB Creator.
iBooks - iBooks is an amazing way to download and read books.