It is easy to open and view Microsoft Compiled HTML Help files (.chm) from Ubuntu. You actually have at least two options: xchm or gnochm.

To install xchm run the following command:

$ sudo apt-get install xchm

To install gnochm run:

$ sudo apt-get install gnochm

To view a .chm file using xchm you just have to run:

$ xchm chm-file

Alternative to open it with gnochm simply run:

$ gnochm chm-file

Or in a simplier way, you can just double-click on the file’s icon.