The Ubuntu Pocket Guide and Reference is a good book to buy (currently less than $10.00 from Amazon) and keep handy while you get started or expand your use of and knowledge about the popular GNU/Linux distribution. It can fit in your pocket, or sit easily beside your computer. What’s more, you can download the PDF ebook for free.

http://www.ubuntupocketguide.com/download.html

The Amazon link is included at the Web page above.