There are several good replies here already so I’ll only add the two following thoughts after reiterating Dieter’s recommendation to get the O’Reilly book on the Bash shell.
[1] If you are not already aware, *nix installs include excellent ‘man’ (manual) pages. If you need an explanation on a command you see referenced, type man and start reading.
[2] Google.
Good luck.
Andy
The really cool thing about Debian, or ubuntu is that if you google “debian / ubuntu howto x.y.z” You will usually come up with very useful information, and several ways to accomplish your task.
This is not only very useful for a complete beginner, but people like me who have been using Linux for a while off and on, but use another OS ( such as windows ) as a primary desktop OS.
In the case of Linux, you could probably get away with not using books thus saving yourself money. And in the case of Bash, there is plenty of good information out there. You can even search youtube, for decent information.