The best book I found for beginners is A Practical Guide to Linux(R) Commands, Editors, and Shell Programming
. I don't personally know anyone else who uses linux so I used it to start my learning from scratch. Now the teachers at my college are coming to me all the time for help with their first linux installs (this is my second time in college). The same author also wrote A Practical Guide to Ubuntu
which I have, it seems to be very similar to the first book. I don't know whether or not to suggest it, but if this is your first time using linux, and you use Ubuntu it could be a better idea, but I would suggest the first book for all distributions.
Be prepared to work hard as Sobell's books are very clear and easy to understand, but he presents some challenges at the ends of the chapter that really challenge you and give you a thorough understanding of everything you are doing.