IMHO You learn linux by playing with linux, not by reading a book.
I'd advice against learning on the iLiad, its too dangerous to brick it if you don't know what you are doing.
If you don't have a dedicated computer I'd eigther go for a virtual machine like VMware or completly new is this cool thing:
https://wiki.ubuntu.com/install.exe/
This will install a linux on your computer WITHOUT need to change your harddisk at all, the linux will reside on a single file within your windows harddisk..