The nutshell books are usually good as reference manuals, rather than teaching/learning guides. As the subtitle of that one says "A desktop quick reference guide"
which is how I use mine, it sits next to the pc, and I look things up when using the command line when "man command" isn't clear enough for me. But it's not the sort of book to work through.
There's plenty of guides on the internet, I've been looking at some of the guides at
http://www.linuxhq.com/ recently. Linux not Unix, but unless you get into the real nitty gritty that may not matter.
this may help to
20 of the Best Free Linux Books - Part 1
if you install Linux at home, you can have a play without breaking any servers
http://www.linuxlinks.com/article/20...oks-Part1.html