This is an useful CHM reader software:
1. view a CHM, you can zoom in or out on their own
2. directory or the index navigation, you can automatically open the last read page
3. add or edit bookmarks, save your favorite CHM files
4. flexible search capability, search in files or index
5.scroll left or right with two fingers for Page navigation
6.pinch with two fingers for zoom in or out page
You can in-app purchase for more function:
1. exported CHM to EPUB, including table of contents (with hierarchical relationships)
2. exported CHM to PDF, including table of contents (with hierarchical relationships)