What are some alternatives?
calibre - Ebook manager, viewer & converter
Kchmviewer - Kchmviewer is a free, open-source CHM (MS HTML help) and EPUB viewer for Unix, Mac and Windows...
Amazon Kindle - Amazon Kindle software lets you read ebooks on your Kindle, iPhone, iPad, PC, Mac, BlackBerry, and...
ExtraCHM - A fully featured reader for Compiled HTML (chm) documents.
FBReader - FBReader is an e-book reader for various platforms. Features:
CHM Reader Pro - CHM Reader Pro is can read CHM file and Convert CHM to PDF.