If you're technically minded and you use Linux, or you're thinking about doing so, Learning Linux Shell Scripting is a useful book to add to your library. Its 300+ pages cover all the important commands and techniques, from basic directory listing to the development of complex scripts.
There are, to be fair, better books available on the subject. But this one is pretty comprehensive and, until 15th March, you can get it for free instead of the normal $36 price. It'll be delivered as a 3 MB PDF file, ready for you to read on your computer.
Head to https://www.tradepub.com/free/w_pacb41/ to request it. You'll need to supply an email address for the download link. You'll also need some other details about where you work, etc, but I'm sure you'll be able to think of something!