ePub Book Readers for Mac (Available in Mac App Store)
Scarlett
This is the app which won my patronage 
Reason: the name (Scarlett reminds me of the Scarlet Letter and Scarlet Pimpernel), the application-icon, and the ability to listen to the eBook.
Bookle
First the history: Bookle app is developed in collaboration by Adam Engst of TidBITS and Peter Lewis of Stairways Software. The book-publisher / author and software pro programmer combination is hard to fail. The app also features a library interface, allowing you to access your books from the app interface itself. In my list of software to try!
Book Reader
There is a nice video where the features are shown:
indiWiz.com is Subhash's look on technology. Needless to say, it is highly biased with eccentric opinions. 