CoolReader is fast and small and lightweight cross-platform XML/CSS based eBook reader for desktops and portable devices.

Supported formats include:

• FB2.
• TXT.
• RTF.
• DOC.
• TCR.
• HTML.
• EPUB.
• CHM.
• PDB.
• MOBI

CoolReader for Mac allows you to read electronic books in numerous different formats. It has a few neat features such as style sheet support, and a lot of customizations for better reading performance.