There are many computer books come with CHM format.
Gnochm is a CHM file viewer. It is designed to integrate nicely with Gnome. Gnochm has some really nice features for viewing chm files.
sudo apt-get install gnochm
Simply click on the Applications menu in the Accessories section to start Gnochm and open your chm files.
How to Convert .chm ?
Under Linux, you can view a CHM file with the xchm viewer. But sometimes that’s not enough. Suppose you want to edit, republish, or convert the CHM file into another format such as the Plucker eBook format for viewing on your Palm. To do so, you first need to extract the original HTML files from the CHM archive.
This can be done with the CHMLIB (CHM library) and its included helper application extract_chmLib.
Install Chmlib in Ubuntu
sudo apt-get install libchm-bin
Convert .chm files in to HTML files
If you want to convert .chm files in to HTML files use the following command
extract_chmLib book.chm outdir
where book.chm is the path to your CHM file and outdir is a new directory that will be created to contain the HTML extracted from the CHM file.
Convert .chm files in to PDF files
First you need to install htmldoc. HTML processor that generates indexed HTML, PS, and PDF.HTMLDOC is a program for writing documentation in HTML and producing indexed HTML, PostScript, or PDF output (with tables of contents). It supports most HTML 3.2 and some HTML 4.0 syntax, as well as GIF, JPEG, and PNG images.
sudo apt-get install htmldoc
If you want to use htmldoc type the following command in terminal
Once it opens you should see similar to the following screen here you can choose the html file and convert them to pdf,ps