How to view CHM files?
How to view CHM files in Ubuntu?
Solution 1:
xChm Viewer 
Install the xChm Viewer for viewing CHM files:
sudo apt-get install xchm
Solution 2:
chmsee is no longer available in Ubuntu, as it is no longer being maintained. Here is the announcement on the project site:
Stop maintain
ChmSee is not being developed anymore.
I haven't read CHM documents more than a year, new and update IT books are pdfs or epubs, so it's right time to end this chm viewer.
chmsee 
https://code.google.com/p/chmsee/
sudo apt-get install chmsee