Keir Thomas has published a new book titled “Ubuntu Pocket Reference and Guide” which can be purchased on Amazon for $9.94 or download for free in PDF format from his website. Keir has a long history in writing quality Ubuntu books and I highly suggest checking this one out! 
A quick excerpt from his website..
At just 5.25 x 8 inches and 164 pages, Ubuntu Pocket Guide and Reference is a compact yet comprehensive guide to everyday Ubuntu use.
It’s ideal for those who need vital information on all aspects of using Ubuntu, but who don’t have time to wade through thick documentation.
Each chapter of Ubuntu Pocket Guide and Reference tackles an aspect of Ubuntu.
First, you learn about installation—getting Ubuntu onto your computer—after which you learn how to configure your computer’s hardware.
Following this, you’re introduced to the Ubuntu desktop, and the tricks and techniques of efficient day-to-day usage. The book then describes the highways of the Ubuntu filesystem, and gives a full run-down of Ubuntu’s file manager.
Next, the command-line is tackled in-depth, after which software management is explained. Finally, system security is described—configuring the firewall, installing antivirus, and encrypting sensitive data. Appendixes provide a glossary of terms, and a guide to understanding technical documentation.
Written for anybody switching to Ubuntu, particularly former Windows users, Ubuntu Pocket Guide and Reference assumes zero Linux knowledge. It provides the wisdom of the expert user and concisely conveys core competencies.