I would suggest you to buy books for ubuntu. There are

I got the following search result from amazon
http://www.amazon.com/s?url=search-alias%3Dstripbooks&field-keywords=ubuntu+linu\
x

For beginners you can start here
https://help.ubuntu.com/


Book is a great thing to start with.

There are a lot of online resources too for more newer problems

http://ubuntuforums.com
OR
http://ubuntuguide.org
OR
any such online forums