Lot of documentations and e-books are now available in chm format. There is lot of tools are available in Linux for reading chm books. xchm, chmsee, KchmViewer , gnochm and archmage .
all of the above utilities are available ubuntu repositories
open a terminal
$ apt-get install xchm
(same way you can install chmsee, Kchmviewer, gnochm and archmage)
or use synaptic package manager for installing
